Chem Final

Short Answer Questions

• Double replacement, net ionic, redox rxtns

• % yield / stoichiometry / limiting reactant

• Gas Laws

• Thermodynamics

• Hess’s Law

Law of Conservation of Mass

Mass can not be created or destroyed

Diatomic elements

Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂

Double displacement

ab + yz → az + yb

Single displacement

a + yb → y + ab

Synthesis

a + b → ab

Decomposition

ab → a + b

Combustion

C_xH_x + O_x → CO₂ + H₂O

Percent Yield

Actual ÷ Theoretical

0 → +2

Oxidized RA

+2 → 0

Reducing OA

Kinetic nrg is directly proportional to ___

temp

Elastic collision

100 % of nrg is transfered, none is lost

(gas) 5 postulates

1. particles are in constant, rapid, straight line motion

   1. result: gases expand to fill their containers shape and volume

   2. gases are fluids

2. collisions between gas particles, other particles, and the container wall are elastic collisions

   1. result: pressure is exerted when the particles hit the sides of the container

   2. Gas pressure is caused by collisions of gas particles

      1. increase of temp causes this

3. the temp in gas (kelvin) is directly proportional to the average kenetic energy of the particles

   1. if temp doubles so does kinetic energy

   2. at same temp- lighter gas particles are faster

4. there are no forces of attraction between gas particles

5. the volume of individual gas particles is nearly zero

   1. result: gases are mostly empty space

Real Gases

Have almost no volume, small amounts of attractive forces, and behave like ideal at low pressure and high temp

Attractive Forces

Solids, then liquids, then gases

crystalline solids

• most solid substances are these

• particles are arranged in orderly, repeating, three dimentional patterns

• shape reflects arrangement of particles

amorphous solids:

• not arranged in any particular order

• like liquid particles but in fixed positions

• don’t have a definite melting point while crystalline solids do

Which of the 3 are fluids

liquids and gases

Solids

• closely packed together in fixed positions

• only vibrate in place

• have definite shape and volume

• forces of attraction are much stronger in solids than in liquids or gases

• lowest amount of kinetic energy

Changes of States of Matter

What does increased temp do to vapor pressure

Increases it

Endothermic (KMT)

liquid + energy —> gas

boiling and evaporation; energy needs to be added

Exothermic (KMT)

gas —> liquid + energy

condensation; energy needs to be removed

Heating & Cooling curve

Phase Diagram

Triple Point

Where the solid, liquid, and gas can exist at equilibrium with one another

Atmospheric Pressure

• Force exerted by the weight of air the atmosphere

• Decreases as altitude increases because there is less air above you

Formula for heat required to melt solid/vaporize (liquid to gas)

Q = mH _fus/vap

Q- heat, m- mass, H- enthalpy (nrg), fus- fusion, vap- vaporization

Endothermic (Thermodynamics)

Heat goes from surroundings to system, temp increases, ΔT is pos

Exothermic (Thermodynamics)

Heat goes from system to surrondings, temp decreases, ΔT is neg

Specific Heat Capacity Formula

Q = mCΔT

Q- heat, m- mass, C- specific heat capacity, ΔT- change in temp

Enthalpy

• State function: look at initial & final not middle

• Heat content of a rxtn

• Heat_final - Heat_initial

Heat capacity

Heat required to raise an objects temp by 1^o C

Calorie

Heat required to raise the temp of 1g/water by 1^o C

Specific Heat

Heat required to raise temp of 1g by 1^o C

Hess’s Law ex. problem

Stoichiometry: Moles to Moles

Moles of atom to moles of diff atom

Stoichiometry: Moles to mass

Times molar mass over 1 mol

Stoichiometry: Mass to Moles

Moles over grams

Stoichiometry: Mass to Mass

Times Molar mass over 1, molar ratio, 1 over molar mass