FINAL REVIEW

1 mole = 6.02 x of anything Molar mass – add up the mass of each element * number of each element CO 2 – 1 * * 16 = 44g/mole To find moles: Grams/molar mass = moles 1 mole of any gas is 22.4 L at STP

Empirical Formula (EF) - “simplest”, the smallest whole number ratio of atoms in a molecule or of ions in a crystal. Molecular compounds often are multiples of a simple formula. For example C 2 H 6 would reduce to an empirical formula of CH 3 Molecular Formula (MF) - “true”, actual number of atoms in a molecule or crystal.

Steps to solve empirical formula 1. Convert grams to moles 2. Divide by smallest number of moles 3. Multiply until all whole numbers

Charges on ions

Diatomic molecules H 2, N 2, O 2, F 2, Cl 2, Br 2 and I 2 Notice that all but H2 form a 7 on the periodic table. You need to know these.

5 th type of reaction – combustion C x H y + O 2  CO 2 + H 2 O

Stoichiometry 1 step problems format of Given * Asked = Asked Given Where: Given is the number of moles of reactant or product in the problem Asked is the number of moles of reactant or product you are trying to find Asked/Given is the ratio in the balanced equation

3 step stoichiometry problems Step 1. Convert whatever unit you are given to moles of given Step 2. Convert from moles given to moles asked (using a balanced equation) Step 3. Convert from moles given to whatever unit you are asked for

Percent yield Percent yield is a measure of how efficient a reaction was. For example: a percent grade on a test measures how well a student answered the questions compared to the actual answers. Percent yield = Actual yield* 100% theoretical yield

Solid – Atoms move, but are held in place. Liquids – particles are free to slide past one another, but are still attracted to one another by intermolecular forces Gases – particles are free to move throughout a container. Far apart and not attracted to one another

GAS PRESSURE Gas pressure - the force exerted by a gas per unit of surface area What causes gas pressure? The collision of gas particles with an object causes pressure. Remember that there are billions of particles hitting a small area at the same time. Kinetic theory assumes that the collisions are elastic – no energy lost

Evaporation Remember, temperature is a measure of the average kinetic energy. Some particles have more kinetic energy Particles with a high enough kinetic energy can break free from the surface and become a gas Particles with lower KE cannot. As highest KE particles leave, Temperature decreases.

Sublimation Under certain conditions, a material can go directly from a solid to a gas. This is called sublimation. Moth balls and air freshener are examples of substances that undergo sublimation.

Ionic solids Ionic compounds are not arranged in molecules, but instead form large crystals held together by ionic bonds. Very strong intermolecular forces = High Melting Point

Heating curve for water

Combined gas law P 1 V 1 = P 2 V 2 T 1 T 2 T is always in K ( C + 273) P and V can be anything, as long as the units are the same.

What happens to the volume As pressure increases? Decreases As temperature increases? Increases As number of moles increases? Increases

Graphs of gas law relationships

Ideal gas law PV=nRT Where P is pressure, V is volume, n is number of moles, T is temperature and R is the ideal gas constant. R = L atm/mol K In this case, P in atm, V is always in L, n is always moles and T is always K

Dalton’s Law of Partial Pressures When 2 or more gases are present in a mixture without chemical interaction (for example nitrogen and oxygen in air) the pressure of the mixture is the sum of the pressures of each of the individual gases. Mathematically P tot = P 1 + P 2 +P 3 +…

Law of Conservation of Energy in any chemical or physical process, energy is neither created nor destroyed. Heat ALWAYS flows from hot to cold Heat continues to flow until temperature difference is zero (both at same temperature).

Energy is required to go from a solid to a liquid or a liquid to a gas at the same temperature. This energy is ∆H of fusion for melting ∆H of vaporization for boiling

Heating a substance in a phase Q=mc  T Changing phase – multiply grams times  H for the phase change.

ExothermicEndothermic ∆H negative ∆H positive Energy is a productEnergy is a reactant Surroundings warm upSurroundings cool Reactants have moreReactants have less Energy than products

Exothermic reaction graph

2 ways to write a thermochemical equation. Energy can be included as a reactant or a product or as ∆H after the equation. 4NH 3 + 5O 2  4NO + 6H 2 O ∆H = kJ 4NH 3 + 5O 2  4NO + 6H 2 O kJ

How much heat is released when 1.0 mol of C 2 H 2 reacts? 1 mole C 2 H 2 * 2500 KJ/2 moles = 1250kJ 2C 2 H 2 + 5O 2 →4 CO H 2 O KJ

Alpha emission U → Th He Beta emission I → Xe e Fission 1 0 n U → n Sr Xe Fusion 7 3 Li He → 10 5 B+ 1 0 n

Penetrating power

Half life