Chemistry Friends/Printable version

Chemistry Friends

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Standards

STP

STP is an acronym for "Standard Temperature and Pressure". STP is 100 degrees Celcius, or 373 degrees Kalvin, and 101.3 kPa.

SATP

SATP is an acronym for " Standard Ambient Temperature and Pressure", which is, simply put, room temperature. It is 25 degrees Celsius (298 degrees Kalvin), and 100 kPa.

Separating Matter

mechanical

To separate mechanically, matter is divided manually or with a magnet(p.38).

settling

Some mixtures can be separated by letting it sit so one substance sinks to the bottom of the container. This method is normally very slow but can be sped up by spinning the container (p.39).

floatation

Air is blown into the compound, causing some parts of it to froth and float to the top. The top portion is then skimmed off (p.38).

filtration

If you have a heterogeneous mixture with solids mixed in it, you can pour it through a filter to separate the solids from the fluids (p.38).

example of a filter

extraction

You can mix something into your solution that is soluble with some of the elements in the solution but not all of them (p.39).

fractional distillation

Fractional distillation is achieved by boiling a liquid compound at different temperatures. The components vaporize at separate temperatures and so they can be separated (p.39).

diagram of fractional distillation process

crystallization

In a compound where a solid is dissolved in a liquid is cooled to form crystals of the solid element. This happens naturally with salt or sugar water (p.39).

chromatography

The mixture is dissolved into a solvent. The solvent goes through a porous material such as filter paper, and the elements of the compound separate at different rates in porous material. This creates rings or lines of different elements (p.39).

classifying matter

pure substances

elements

Everything is made up of elements. We are mostly carbon, hydrogen, oxygen, nitrogen, calcium and phosphorus. Elements consist of: protons, electrons, and neutrons. Neutrons and protons stay in the nucleus while the electrons orbit around.

compounds

When two or more elements are combined with definite proportions they are known as compounds . Water (H2O) and salt (NaCl) are both compounds because they are made of more than one element.

mixtures

homogeneous mixtures

In a homogeneous mixture, you can't see the separate components. The prefix "homo" is used, because it indicates sameness. Homogeneous mixtures are often called solutions, or when the particles are slightly bigger, colloids. The particles in a homogeneous mixture are invisible to the naked eye, except for certain colloids where the particles may be seen if in a direct shaft of light .Metals such as stainless steel and bronze are homogenous mixtures.

heterogeneous mixtures

Heterogeneous mixtures are mixtures where the different components are visible to the naked eye, "hetero" indicating difference. Suspensions are heterogeneous mixture that, when allowed to sit, will separate into their different components. Mixed vegetables, beach sand and oil-vinegar mixtures are all examples of heterogeneous mixtures .

Elements

Classifying elements

There are a few ways to write the names for molecules. Every element on the periodic table has a name and a symbol. For instance, you can write the element hydrogen in two ways. Either you can just write out the name hydrogen, or you can write its symbol,H. The symbol is one or two (and in some cases, three) letters. The first letter is capitalize and the next is small.

Naming Ionic Compounds

When elements stick together in an ionic compound, there is a special way to write the compound. Say the is a compound of zinc and oxygen. Its names would be 'Zinc oxide' when writing the name, we change the last syllable of the last element to -ide. When you write the chemical formula, you use the symbols instead of the whole word. Also, you need to specify how many zinc and oxygen atoms are in each compound. Zinc has a charge of 2+ while oxygen is 1-. In order to make a stable compound, you want the charges to add up to zero. So you'd need two oxygen atoms for every zinc. This is the chemical formula: ZnO₂. When naming an ionic compound with its full names, you don't need to say the amount to each element but you do if you are writing the symbols.

Naming Molecular Compounds

Naming molecular compounds is very similar to naming the Ionic ones. However, when naming the compound you need to specify how many of each atom there are. For instance, water's chemical formula is H₂O. We write its full name dihydrogen oxide. we put the prefix 'di' on the hydrogen to say that there are two hydrogen atoms on each oxygen. Here's a list of the prefixes 1-10 ( pg.113)

1. mono (you don't really need to write this, but you can.)
2. di
3. tri
4. tetra
5. penta
6. hexa
7. hepta
8. octa
9. ennea
10. deca

Periodic table

periodic law

The periodic law is a law about the arrangement of elements according to their mass discovered by John Alexander Newlands in 1864. It stated: "When elements are arranged in order of increasing atomic mass, chemical and physical properties form patters that repeat themselves at regular intervals". (p.63).

family/group

The periodic table is divided into eighteen different columns, known as "families" or "groups". Each family of elements have similar characteristics, such as the number of electrons in their outer orbital or the way they react with other elements. The first family, which includes Sodium and Francium, have only one valence electron and all react violently with water.

alkali metals

Alkali metals are the metals in the very first group on the periodic table, on the far left side, excluding hydrogen, which is merely in that row for organizational purposes. Every element in this family have an ion charge of 1+, and have only one valence electron. This means that they are highly unstable and react very quickly with other elements. Alkali metals are especially reactive with water. The higher their atomic number, the more violently they react because they are more unstable. Rubidium and Potassium are both alkali metals.

alkaline-earth metals

Alkaline Earth metals are the elements in the second family, near they left side of the table. They have an ion charge of 2+ and they are quite reactive.

transition metals

All the metals from the third group to the staircase line are known as "transition metals". They have varying ion charges, with some of them having more than one, and they have varying levels of reactivity. This section of elements contain many of the metals that we use daily, such as iron, copper, and tin.

halogens

Halogens are the non-metals located on the second last family of the periodic table, near the far right side of the table. They are highly reactive elements because of their ion charge of 1-.

noble gases

Noble gases are the gases in the family to the far right side of the periodic table. They are known as "noble" because they are the only elements with a full valence shell, and as such they will not react with other elements easily. They are elements that are stable in normal conditions. These elements light up in different colours when an electric charge is passed through them. Helium, Neon and Argon are all noble gases.

lanthanides

The series of elements that starts after Lanthanum is called Lanthanides

actinides/transuranic

The series of elements that start after Actinium is called Actinides.

staircase line

This is the line between the metals and the nonmetals. It is called the staircase line because it resembles the steps of a staircase,

Metals

Metals are found on the left side of the Periodic Table.

Nonmetals

These are found on the right side of the staircase line.

Atomic theory

Early Greek Theories

The early Greeks only had the technology available to identify a few elements. The first seven elements identified were gold, silver, iron, mercury, tin, copper and lead. At the time, the Greeks only knew of seven planets or celestial bodies, and so gave each of the elements a celestial body and a symbol to represent them. The Greeks knew very little about the chemical properties of the elements, they merely used them for making tools and art. As time went on, it became apparent that having symbols would not be sufficient for all the elements, and so it was eventually changed to letters. (p.55).

Dalton's Atomic Theory

Dalton's theory is often called the billiard ball theory. He believed that atoms were neutrally charged spheres, with no real distinction between protons and electrons.

Bohr's Theory

Bohr was the first chemist who theorized that elements have a positively charged nuclues with negatively charged electrons orbiting around it, where the electrons were divided into orbital groups, with a specific number of electrons in each shell. He figured that there would be a certain number of electrons in each orbital, and the number of electrons in the last shell would determine the chemical properties.

Electrons

Electrons are negatively charged. They orbit around the nucleus. Each orbital requires a certain amount of electrons. When there aren't enough electrons to fill the orbital, the atom is positive. When the opposite happens and the atom has to open up a whole new orbital just for one or two little electrons. This atom is negatively charged. When a positively charged atom such as a sodium finds a negatively charged atom like chlorine, the chlorine gives his extra electron to the sodium who needs an extra one. Then the two of them become an ionic compound, sodium chloride.

Nucleus

The nucleus is the center of an atom. It comprises of both the positively charged protons and neutrally charged neutrons. It is the nucleus of the atom that makes up most of the weight of the atom, because electrons do not weigh enough to be significant. Each proton or neutron weighs 1 AU (Atomic Unit). You can find out how many protons or neutrons there are in an element by looking at the molar mass and the atomic number. The atomic number will be the number of protons, and the atomic number subtracted from the molar mass will be the number of neutrons.

Atomic Number

The atomic number is the number of the element on the periodic table. It signifies how many electrons are orbiting the nucleus of the element, so as the atomic number gets higher, so does the number of electrons. For example, Carbon's atomic number is 12. That means it has 12 electrons, and therefore 12 protons. Elements are grouped together based on their atomic numbers, because the number of electrons an element has can affect it's properties.

Neutrons

Neutrons are the sub-atomic particle that has a neutral charge. They are located in the nucleus of the atom and weigh 1 AU. The number of neutrons in an element determine if it is an isotope or not.

Isotope

An Isotope is an element with the normal number of protons and electrons, but has extra or fewer neutrons. The element is still neutrally charged because the protons and the electrons are still balancing each other out. The extra or missing neutrons add or subtract weight to the element. Isotopes can be found in nature, but they are generally not as stable as the normal version of the element. (p.76).

Mass Number

The mass number is the molar mass of an atom. It comprises of the combined mass of both the protons and the neutrons of the element. On the periodic table, the molar mass will rarely be a round number. This is because it is the average mass of all common isotopes of the element. Hydrogen has very few common isotopes, so it's atomic number is 1.01.

Monoatomic Ions

Monoatomic Ions are elements that have either gained or lost electrons to fill their valence shell. This makes them have either a positive or negative charge. They are also known as ions .

cations

Cations are elements that have lost electrons to fill their valence shell. They have a positive charge as an ion because they have more protons than they do electrons. All alkali metals are cations because they will lose electrons rather than gain them to fill their last shell.

anions

Anions are the opposite of cations in that they have a negative charge because they have gained electrons to fill their valence shell. Most non-metals will be anions because they are near the right side of the periodic table and will gain electrons rather than lose them. A goofy trick to remember which is which is to visualize a happy cat. This will help you remember that cations are positively charged.

Quiz

Here is a short quiz on the Matter section:

1 In a homogeneous mixture, you can...

	Never see the particles of the different substances
	Always see the particles of the different substances
	Only see the particles that are large enough in certain conditions
	See the particles some days and not others, depending on the humidity

2 What would be the most practical way to separate aluminum cans from garbage?

	Fractional distillation
	Mechanical separation
	Crystallization
	Filtration

3 On the periodic table, the horizontal rows are known as "Families'" or "Groups".

	True
	False

4 Someone had saltwater that they needed to change to pure water and salt so they boil the water. The salt stays in the pot and the person somehow collects the water vapor which condenses into pure water. This procedure is called:

	fractional distillation
	extraction
	filtration
	chromatography

5 Which family of elements is located on the far left side of the periodic table and has an ion charge of 1+?

	transition metals
	noble gases
	alkali metals
	alkaline earth metals

6 Dalton believed that elements were neutrally charged spheres.

	True
	False

7 the molar mass of an element is the mass of: (click all that apply)

	electrons
	protons
	neutrons
	ions
	average of the most common isotopes
	number of electron orbitals

8 When a ion has taken one more electron to complete his orbitals, the molecule is negatively charged.

	True
	False

9 Which monoatomic ion is positively charged?

	anion
	carbon
	cation
	isotope

Ionic bonds

An Ionic bond is a bond where one element give away electrons to another element. This makes one element positively charged and the other negatively charged. Ions are elements who have gotten rid of or gained electrons. For instance, sodium has one electron in its valiant cell. This electron is very inconvenient so the sodium just gets rid of the extra electron. Then, sodium has 11 protons and 10 elections. This makes sodium 1+.

polyatomic ions

These are ions that work together like one ion. If you had NaNO₃, The Na would have bonded with NO₃ and not three Os and an N. This is because these elements work together lie one ion.

Ions of Multi-Valiant Metals

When working with an ion that can have different numbers of protons, the valences need to be taken into account. If you have an iron oxide compound, it could either be FeO or Fe₂O₃. When the iron has a charge of 2+, then it bonds with the oxygen (which has a charge of 2-) with one of each. This makes FeO. If the iron has a charge of 3+, then it has to from with the oxygen with two irons and three oxygens. Thus creating Fe₂O₃.

Covalent bonds

Covalent bonds are elements that borrow electrons. Oxygen needs two more electrons to fill his valiant shell. When he bonds with another oxygen he solves this problem. The first oxygen borrows two of the second oxygen's electrons some of the time and the second oxygen uses two of the first oxygen's electrons. This isn't as strong of a bond as an ionic bond.

polar covalent bonds

When oxygen forms with two hydrogens, it forms water. Oxygen is more negative than hydrogen. Since opposites attract and things with the same charge repel each other, the hydrogens are on opposite sides of the oxygen. The different poles on a covalent bond make it interact differently with other compounds like itself. When water is in liquid form, the molecules slip by without too much difficulty. The opposites of different compounds do attract a bit, but nothing crazy happens. However, when the compound freezes, something crazy happens! Usually elements bunch up together and become more dense than the liquid, but that is not the case with polar covalent bonds. The elements with the same charge refuse to be bunched together. Instead, they form this large, intricate matrix where the opposites touch but nothing else does. There is lots of empty space in between the elements so the solid is much less dense than the liquid. That is why ice floats in water and iron sinks in molten iron.

Properties and Patterns

When elements are in their gaseous form, they follow the following rules.

1. They fill their container but don't have a volume of their own.
2. They are very compressible and can be pushed into a space much smaller than usual.
3. They mix through the air without being mixed
4. When they get hotter they expand

Pressure and Volume

Pressure is force per unit of area. If you had a book with a large area and pushed it softly, it might have the same amount of pressure as a pin if you pushed it really hard. The SI unit for pressure is the kilopascal. One kilopascal (kPa) is equal to 1000 newons of force over 1 square meter. Or 1kPa=1000N/1m². We experience pressure every day. When we lay in our bed the blanket pushes us down. When we sit down for breakfast, we up pressure on our chairs. Even the air had pressure. This is called 'atmospheric pressure'. The average Atmospheric Pressure at sea level is 101 kPa. We call this (101 kPa) 'one standard atmosphere' or 'atm'. When the conditions are all normal and the temperature is 0°C and the atmospheric pressure is at atm, we call it 'standard temperate and pressure' or 'STP'. When the pressure is 100 kPa and the temperature is 25°C it is called 'standard ambient temperature and pressure" or 'SATP'. Just remember that STP has less letters and less heat while SATP has more letters and more heat.

Boyle's law

Robert Boyle was an English chemist. He developed the law about pressure and volume. He realized that if you compress a container of gas the volume will decrees with the same proportions. If you doubled the pressure, the volume would be halved. This is the equation.

v₁p₁=v₂p₂

The first side of the equation is how things where initially, (v=Volume and p=Pressure) the second side is how the Volume and pressure were after they changed.

Temperature and Volume

Jacques Charles was a French physicist. He noticed a relationship between the temperature of a gas and its volume. He noticed that as the temperature of a gas increased, the volume increased proportionately. This can be shown in a few different equations.

v=kT

The v represents volume, the T is temperature and k is a constant value. We can also write the equation like this.

v₁/T₁=k and this v₂/T₂=k

Or it can be simply written together like this:

v₁/T₁=v₂/T₂

The Combined Gas Law

Charles and Boyle both made useful formulas to calculate the changes in gasses. If we combine their theories, we can make a very useful formula that can help us calculate anything we need to know about gasses. The formula looks like this.

p1v1/T1=p2v2/T2.

The letters stand for volume (v), pressure (p) and temperature (T). The nice thing about this equation is that we can customize it to fit our question. If the pressure remains constant we can take it out of the equation and simply write:

p₁v₁=p₂v₂

Kelvin Temperature Scale

Scientists use the Kelvin Scale when measuring temperature. It is written in Kelvin and not degrees Kelvin. When converting Celsius to Kelvin, add 273°C. So if we wanted to know how hot it was on a day in the summer, we'd add 273°C to 25°C. That day, it would be 298 K outside! When writing in Kelvin, the temperature is always a positive number. Not even insanely cold temperatures are negative. This is because 0 Kelvin is Absolute Zero. No where in the universe are things that cold or colder. Absolute Zero means the particles themselves have stopped moving. Even in space the stars keep things from getting that cold.

Avogadro's Theory and Molar Volume

Before a theory is accepted, experiments have to be done to prove it. If an idea helps explain lots of unknown phenomena, it is even better. If you walked into you house and saw your grandmother's shoes on the shoe rack and heard her voice coming from the living room, you may come up with a few theories. One, your grandmother came to visit or two your grandmother left her shoes on the shoe rack when she was sneaking through your house last night and the voice in the living room is a parrot that can mimic voices. You would probably got with theory one: If you conclude that your grandmother is over it explicates two things. Also you may have observed that your grandmother drops by a lot in the afternoons. Theory two makes less scene. You have never known your grandmother to be a forgetful person or go any where at night. Also, you don't own a parrot. If a theory explains lots of things, then it usually makes more sense. The kinetic molecular theory was accepted amoung scientists for this reason. It explains why gases are compressible and why there's gas pressure. It also complements Boyle's and Charles's laws.

The Law of Combining Volumes

Joseph Gay-Lussac was a french scientist. He discovered the Law of Combining Volumes. The law says that if you combine gases the ratio of molecules is in simple whole numbers.

Avogadro's Theory

Avogadro found the reason for the simple ratios. His theory states that if you two containers containing equal amounts of gas at the same temperature, they would have the same amount of molecules. (I don't know how he proved this but I doubt he counted them all.)

The Law of Combining Gas Volumes

Because of the Law of Combining Volumes and Avogadro Theory, we have a simple way of figuring out the amount of each molecule in an equation. Say we knew that hydrogen and oxygen make dihydrogen oxide or in other words:

O₂ + H → H₂O

According to the Law of Combining Volumes, the number of dihydrogen oxide molecules should be a simple whole number. Right now, the equation is wrong. It says two oxygen atoms plus one hydrogen atom equals two hydrogen atoms and one oxygen atom. We still need to balance the equation. Let's start with oxygen. There is one oxygen atom needed in dihydrogen oxide but it is in groups of two on the left side of the equation. Therefore, this equation makes two molecules of dihydrogen oxide. Now for the hydrogen. Since we've decided that there are two molecules of H₂O, that means there are four hydrogen atoms needed. So there are four atoms of it on the left side of the equation. It will look like this:

O₂ + 4H → 2H₂O

Molar Volume of Gases

A mole is a number of particles. It's a bit like saying a dozen but it's a more complicated number. The molar volume of a gas is one mole of the gas at a specific temperature. This volume doesn't change between gases. A gas at STP has a molar volume of 22.4 L/mol. Scientists like to use moles a lot. Working with volume is easier than mass. It is also more exact. You can use molar volume to convert between moles and liters.

Classifying Solutions

A solution is when two or more things mix together homogeneously. These things are called the solvent and the solute. Solutes can be solid, liquid or gas. One of the most popular solvent is water.

Solutions of Electrolytes and Non-Electrolytes

An electrolyte is an aqueous solution that conducts electricity. Pure water isn't an electrolyte, but if you dissolve something in water, it can conduct electricity. Acids and bases are electrolytes. Molecular compounds usually aren't.

Acidic, Basic, and Neutral Solutions

Solutions can be acidic, basic, or neutral. The stronger the acid, the more elecricly conductive it is.

Understanding Solutions

When something is dissolved into a solution, the compound dissociates. This means each molecule and ion goes off in its own with water. If you put NaCl in water, in would dissociate and become Na⁺ and Cl^-. The sodium chloride wouldn't be separated, the ions would just get farther apart. Dissociation makes solutions electrolytes. The Na is positive and the Cl is negative, so if they are dissociated in water, the charges help electricity flow through the solution. This works with acids and bases too. If an acid or base dissolves, it dissociates. Then one of the ions is negative and one is positive.

Substances in Water

Some things dissolve in water better than others. Ions' solubility is very predictable. There are tables to show how soluble different ions are. Molecules are trickier. There is no simple was to predict how soluble different molecules are. You just have to remember.

Reactions in Solutions

Chemicals are put into solutions to make it easier to transport, load and store them. It also helps with reactions. If something is in a solution, it can have a faster, more complete reaction and can change the results. Reactions are faster and more complete for this reason: a dissolved chemical has more surface area than if it were on its own.

Net Ionic Equations

Let's say you have sodium oxide and chlorine and you mix it into a solution of sugar water. The equation might look like this.

Na₂O_(aq)+C₆H₁₂O_6(aq)+ Cl_(aq)= NaCl + C₆H₁₂O_6(aq) + O_(aq)

Now we put the theory of dissociation into effect.

Na_2(aq)+O_(aq)+ C_6(aq) +H_12(aq) +O_6(aq) +Cl_(aq) =NaCl + C₆H₁₂O_6(aq) + O_(aq)

The thing is, this equation seems pretty cluttered and some of the ions don't even seem to change. Let's cancel them out!

Na_2(aq)+O_(aq)+ C_6(aq) +H_12(aq) +O_6(aq) +Cl_(aq) =NaCl + C₆H₁₂O_6(aq) + O_(aq)

This leaves us with the equation

Na_(aq)+ Cl_(aq)= NaCl_(aq)

That makes more sense!

Qualitative Chemical Analysis

There are two kinds of measurements: qualitative and quantitative. Qualitative is looking at litmus paper to see if it is blue or red, noticing bubbles in a solution and seeing rust is forming. You can see results but there are no units or numbers you can put in. That's what quantitative measurements are. A pH of three, twenty seven grams of HCl and two moles of oxygen are all quantitative. They are more exact than qualitative measurements.

Qualitative Analysis by Colour

Some substances can be identified by colour. The colour of the solution might change, there might be a coloured gas or a flame. Litmus paper changes colour based on if the solution it is placed in is acidic or basic. When burned, copper(II) has a green flame.

Concentration of a Solution

If a solution has very little solute in it, it is a dilute. If a substance has lots of solute in it, it is a concentrated solution.

Communicating Concentration Ratios

Use this ratio to find the concentration of a solution.

concentration=quantity of solute /quantity of solution

If there are 2 mL for every 100mL of solution, the ratio would be:

2mL/100mL and the answer would be 2% v/v.

The v/v thing means volume to volume. Some times you need to calculate w/v which is weight to volume. This would be like if there were 4 grams of sugar in a 100mL sugar water solution. There are ways to express very small units. Parts per million is one. If there was three grams of salt in a million mL lake, the concentration of salt would be 3ppm. There is a ratio to find the molar concentration. It is the amount of the solute in moles when dissolved in a liter of water.

Molar concentration= amount of solute (in moles)/ volume of solution (in liters)

Molar concentration is measured in (mol/L)

Calculations Involving Concentration

In chemistry, it is nice to know the quantity, volume and concentration of a solution. If you only know two of these things, you can use a formula to figure the thrid one out.

mass/volume=concentration

Preparation of Standard Solution from a Solid

Standard solutions are solutions with a precise concentration.

Preparation of Standard Solution by Dilution

Dilution is a way of changing the concentration of a solution by adding more of the solvent or some other liquid. If your lemonade is too strong, you might try adding water. This would be diluting the lemonade. Dilution is a pretty easy was to alter the concentration of a solution. Diluted solutions are used a lot today. If a chemical reaction happens too fast, a chemist can dilute the chemical and slow down the reaction. If a doctor needs to prescribe a thousandth of a mL of medicine to you, he might instruct you to take a mL of the medicine, mix it with a L of water and take a mL of the solution. It is easier to measure in milliliters and liters than it is to measure in thousandths of a milliliter. There are many tools to make exact measurements. Volumetric flasks like graduated cylinders and beakers and scales are very common tools. Another tool is called a volumetric. It is a long tube that looks like an eye dropper except the measurements on the side have 0 on the top and the biggest number on the bottom. To use, you fills the tube all the way to the zero and moves the volumetric over the container you want the measured solution in. Since the solution reaches the 0 mark, no solution has dropped into the container. Let's say you need three units of solution. Jiggle the nob on the top of the tube. This lets little bits of air into the tube so the solution drips out the bottom. Carry on until the solution line drops to the three. Put the volumetric away and you have 3 units of solution!

Calculating Dilution

It isn't too hard to calculate a concentration of a solution after it has been diluted. If the amount of solvent doubles, the concentration halves. There is a simple formula to figure it out.

v_ic_i=v_fc_f

The v_i is the volume before you diluted the solution. v_f is the volume after the solution was diluted. c is for the concentration. i for initial and f for final. As long as you know three of the pieces of information, you can use the equation to find out the fourth one.

Solubility

Every solution has a limit to how much of a solute can be added. If more than the limit is added, the access won't dissolve. It'll just sit there.

Solubility Rules and Examples

When mixing substances, there are rules the solutions follow. They are nice to know so you can dissolve things better.

• If you heat water to a higher temperature, more solids solute can dissolve into it.
• If you want to get more gas to dissolve in the water, cool it down. Gas always dissolves better in cold water.
• Gases also dissolve better at high pressure.
• Some oils won't ever dissolve in water because they are immiscible. It's pretty much imposable so don't bother trying.
• The opposite to some thing that is immiscible is something that is miscible! This means there is no limit to how much of the substance you can dissolve. Well, the limit is how much of the substance you can get your hands on.
• Most elements don't dissolve well in water, but halogens and oxygen do alright. Also, metals from group I and II can dissolve pretty well.

You can see evidence of solutions all around. If you let the water evaporate from the solution, any solid solutes left behind form crystals. Stalagmites and stalactites are good examples of left behind minerals. You might also notice that when you open a can if pop, some air escapes. What that is is carbon dioxide that use to be dissolved in the drink when it was cold, but undissolved as the pop warmed up. Fish survive because of the oxygen dissolved in the water.

Concentration of Ions

Moles of Ions and Ionic Compounds

In chemistry, it can be very useful to know the molar concentration of ions. First, let's remember that a mole is a number, like a dozen. It isn't an amount, it is a number. A complicated number, but a number none the less. So if we have one mole of an ion like CaCl₂, There is one mole of CaCl², one mole of Ca, and 2 moles of Cl. Just like if there were a dozen cats, there would be a dozen tails, two dozen eyes and four dozen paws. (Unless, of coarse, there were any mutant cats with three eyes or unfortunate cats who lost an eye.)

Molar Concentration

So anyway, another thing we need to know is the symbol for molar concentration. It is square brackets. So [NaCl] is the molar concentration of sodium chloride.

Calculating Molar Concentration

When we calculate molar concentration, we dissociate the ions and calculate them separately. So let's say we are looking for the molar concentration of CaCl₂ in a 0.123 mol/L solution. First thing we do is dissociate the ions.

CaCl_2(aq) → Ca_(aq) + 2Cl_(aq)

Let's find the molar concentration of Ca first! We multiply the concentration by how many moles there are. In this case, there is one mole.

[Ca_(aq)] = 0.123 mol/L × 1 = 0.123 mol/L

So, There are 0.123 mol/L of carbon in the solution. Now for the chlorine. Remember, there are 2 moles of chlorine.

[Cl_(aq)] = 0.123 mol/L × 2 = 0.246 mol/L

There are 0.246 mol/L of chlorine!

Molar Concentration of Hydrogen

It is very important to know the molar concentration of hydrogen ions because hydrogen ions make acids. The higher the hydrogen concentration, the more acidic the solution. Pure water is neutral. It has a pH of 7. What this means is the hydrogen concentration of water is 1×10^-7 mol/L. Something more acidic, like vinegar, has a pH of about 2 and therefore a hydrogen concentration of 1×10^-2. Something basic with a pH of 11 would have a hydrogen concentration of 1×10^-11.

Acids and Bases

Acids and bases are compounds that one or more "loose" hydrogens (H) or hydroxides (OH) attached to them. These hydrogens or hydroxides do not have a very strong bond to the compound, and they will break free very easily. It is the hydrogens and hydroxides, that give acids and bases their properties.

How Our View of Acids and Bases Changed

People have noticed differences between acids and bases for ages. Differences between the two had been noticed since the middle ages. Discoveries about the pH scale and acid-base reactions began in the early 1900s.

Most of the early theories about acids and bases weren’t right but at least they were trying. In the mid-seventeen hundreds, a guy named Antoine Lavoisier came up with a theory. He concluded that oxygen and water made things acidic. Sulfuric acid was H₂SO₄ which could be made of H₂O and SO₃. So He thought it oxygen made it acidic. This wasn’t the case. Some solutions with oxygen in them, like CaO and are basic. There are also acids without oxygen in them.

A guy named Sir Humphrey Davy concluded that Hydrogen was responsible for acidity. Another guy by the name of Justus von Liebig agreed with Humphrey and elaborated the theory. He hypothesized that hydrogen can form ionic bonds were the hydrogen act like the metal. He decided that acids were the salt of hydrogen. This was a good theory, but it didn't explain why loads of compounds with hydrogen in them are neutral, like water or basic, like NH₃.

At last in 1887, Svante Arrhenius came up with a pretty good explanation. He concluded that acids were ionized in an aqueous solution. In the solution, they formed bond with the hydrogen ions. Bases did the same thing, except they formed ionic bonds with hydroxide. This might have been a little off, but it did explain somethings, like water being neutral. Because H₂O is a combination of Hydrogen (H⁺) and hydroxide (OH^-), it is neutral.

Revising Arrhenius' Definition

Arrhenius was right about acids dropping hydrogen ions and bases picking up hydrogen ions but that theory wasn't complete. When acids drop hydrogen, it doesn't stay a lone hydrogen for very long, if there is any water nearby, the positive hydrogen ion will be attracted to the slightly negative side of the oxygen atom and forms H₃O⁺. This is not a covalent bond. The hydrogen is just attracted to the slightly negative oxygen.

Hydrolysis of Amphoteric Ions

Amphoteric ions are things that alone are not acidic or basic but, it will become so if you just add water. Take NaHCO₃ for example. Alone, it doesn't look too acidic but, if you mix it in water, the sodium will disconnect. It's still close to the rest of the ions, still technically bonded to the HCO₃. It's kind of like at a dance, if your not holding hands with your dance partner, your just close by. Then, something happens in the solution. The water wants to bond with the HCO₃ so they just leave the Na there. It would be like if one of the dancers found someone else to dance with and just left. Really rude. Anyway, the HCO₃ and the H₂O bond, forming OH^- and H₂CO. The OH^- is of course, a base. Another example is NaHSO₄. In water the Na is again, dissociated with the ion and H₂O comes in. They form HSO₄ and an extra hydrogen (acid). This hydrogen finds some water and makes H₃O.

Hydrolysis of Metal and Nonmetal Oxides

These are a lot like Amphoteric ions except there simple metal and nonmetals instead of polyatomic ions. There is just a simple rule for these: If a metal ion is mixed with water, it makes a basic solution. If the compound is nonmetal, it forms an acid.

Hydrolysis of Metal Ions

When a metal ion is mixed into a water solution, bonds with the water to form complex ions with the water. These will drop hydrogen in the water to make an acid.

Predicting the Results of Hydrogen

There is a way to find out the concentration of an acid (usually hydrogen). See, in a reaction not all the chemicals react. If you mixed Na and Cl, you'd get a lot of NaCl and also some lone Na and Cl. This equation shows us what the concentration is: K_a× K_b=K_w. Say you have a reaction like HF + H₂O → H₃O + F. K is HF × H₂O/H₃O × F. Since H₃O is an acid, K is replaced by K_a which is basically the same thing, it just specifies that we're finding the acid concentration. If we use K_b we are looking for a base. K_w is water. So say we have the reaction, CO_3(aq) + H₂O_(aq) → OH_(aq) + HCO_3(aq). If we know that there is a 0.100 mol/L concentration of CO₃ and the pH is 11.66. Since we are working with bases, we will use K_b. To find the concentration, we multiply each side of the equation and divide the sides. We divide the side of the reaction with the base by the side without the base. It looks like this:

K_b = [OH] × [HCO₃]/ [CO₃]

Notice, we don't put water in the equation. This is because everything is dissolved in water and the CO₃ concentration is measured in moles per liter of water. Now, let's put some numbers in the equation! We know the pH is 11.66, this means the pOH is 14 - 11.66 or 2.34 or 10^-2.34. If we turn 10^-2.34 into a proper exponent, we will know the concentration of OH. If you put 10^-2.34 in your calculator, it will come out as the proper exponent: 4.57×10^-3. This is the concentration of OH and since there is an equal concentration between OH and HCO₃, the number is also the concentration of HCO₃. Now we know the three numbers needed!

K_b = (4.57 × 10^-3)(4.57 × 10^-3)/ 0.100

K_b = 2.0 × 10^-4

Measuring Acids and Bases

The pH Scale

Acids and bases are measured on something called the pH scale. It is a scale going from 0 to 14, where 1 is the most acidic and 14 is the most basic. 7 is in the middle of the scale, and so it is neutral.

Everyday solutions have different pH levels.

Hydrogen Ion Concentration

The pH scale measures the relative concentration of hydrogen in a compound. Starting at seven, each level of the scale going up or down represents 10 times more concentration of hydrogen. Therefore, a pH level of 6 is ten times more acidic than one of 7, and a pH level of 5 is one hundred times more acidic than seven. Alternately, a pH level of 8 is ten times more basic than one of seven, and so on. This is what is known as a logarithm. In this case, it is a negative logarithm, because acids have a higher concentration of hydrogen than bases. This principle can be applied to help you know the pH from a hydrogen ion concentration. If you are given an Hydrogen concentration of 0.000006 M. You can find it's pH by converting it to scientific notation. The decimal place has to move back six times, so the scientific notation would be 6.0 x 10^-6. This means you multiply 6.0 by negative 10 six times, and therefore if it were a pH it would be one of 6. Reference: The virtual chembook (to be added as actual reference)

Naming Acids

Depending on what cation the hydrogen is attached to, acids will have different names. Simple acids, known as binary acids, have only one cation and one hydrogen. These acids are named by taking the prefix hydro, then putting the first syllable of the cation, then the suffix -ic. For example, HCl, which is hydrogen and chlorine, is hydrochloric acid. More complex acids are acids that have oxygen in the compound. There is a simple rule for these acids. Take nitrate (NO₃) for an example. Any polyatomic ion having the suffix -ate uses the suffix -ic as an acid. So HNO₃ will be nitric acid. When you have a polyatomic ion with one more oxygen than the -ate ion, then your acid will have the prefix per and the suffix -ic. With one less oxygen than the -ate ion, it will have the suffix -ous. With two less than the -ate ion, the prefix will be hypo and the suffix will be -ous. Example: (some of these acids do not exist and are only used for example purposes)

  Nitrate > HNO3 >Nitric Acid.   
  One more Oxygen > HN2O4 >pernitric Acid. 
  One less oxygen > HNO2  >Nitrous Acid.
  Two less oxygen > HNO  > Hyponitrous Acid.

The Acid-base Concepts of Bronsted and Lowry

Both Bronsted and Lowry came up with a theory to explain how acids and bases work. Acids are compounds that will drop hydrogen ions. These loose hydrogens will proceed to bond onto other compounds. Bases are the opposite; they pick up hydrogen ions. Stronger acids drop hydrogens easier than weak acids. Strong bases take hydrogen ions more than weak bases. The really strong bases will take hydrogens from compounds that don't want to give up their hydrogens.

Conjugate Acids and Bases

After a strong acid gives up its hydrogen, it becomes a weak base. Redundantly, a strong base becomes a weak acid after it gets a hydrogen. There is a simple explanation for this. An acid has a hydrogen and has a bond with it. The bind may be weak, but it is a bond none the less. After the acid get rid of the hydrogen, it doesn't really want to get another one, but it does have room for the bond. It works just opposite to that with bases.

Acid-base Indicators

When a substance changes colour when it is mixed with an acid or base, it is called an acid-base indicator. Litmus paper is the most common type. When you put a piece of litmus paper in an acid, it turns red. When you put it in a base, it turns blue. Remember: Acid Red, Base Blue.

Buffers

A buffer is a solution that will keep something at about the same pH. For an acid, it is a weak base and for a base, it is a weak acid. When you mix the buffer to an acid so the solution is about half acid and half buffer, it is acting as a buffer. During this time, the acid is giving its hydrogen ions to the base buffer. However, when all the hydrogen ions are taken by the buffer, the solution reaches the buffer capacity. Then, if you add any more of the buffer, the pH will just go up to the pH of the buffer.

Quantitative Relationships in Chemical Changes

In quantitative relationships, you can use a balanced chemical equation and knowledge about how much of a substance there is to find out what substance you will have too much of, what you will run out of and how much of a substance you will need. Limiting Reagent is the substance that runs out, and excess reagent is the substance you have leftovers of.

Gravimetric Stoichimetry

Gavemeter is determining solid reactants by weight.

Gas Stoichimetry

When using gas stoichmetry determine the amount of gas used by volume. The STP (standard temperature and pressure) is 22.4 L/mol. The SATP (standard ambient temperature and pressure) is 24.8 L/mol. A formula you can use with gas stochimetry is pv=nRT. 'p' is pressure, 'v' is volume, n is moles (not moler mass) 'R' is the constant (8.31 kPa×L/mol × Kalvin) and 'T' is the temperature in Kalvin. You use this formula to find any one of the reactants.

Chemical Analysis By Titration(Solution Stoichimetry)

Titration is determining liquid reactants by mol/L. In titration, we know the concentration of one the reactants. One way of finding the concentration of one of the reactants is by adding the reactant with the known concentration to the reactant with the unknown concentration a little bit at a time using a buret. When the reactant with the unknown concentration fully reacts with the other reactant, you can check the buret to see how much known reactant you used. then look at the balanced chemical equation to calculate the concentration of the reactant.