Semester 2 Final Exam

Question 1

Empirical Formula

Answer 1

Simplest whole # ratio of atoms in a compound

Question 2

Molecular Formula

Answer 2

Actual formula (which is a whole multiple of the empirical formula)

Question 3

Molecular: H2O

Answer 3

Empirical: HO

Question 4

Molecular: C6H12O6

Answer 4

Empirical: CH2O

Question 5

Molecular: C6H6

Answer 5

Empirical: CH

Question 6

How to find the Empirical Formula

Answer 6

1) Find the moles of each element

2) Determine the mole ratio (Largest/Smallest)

Question 7

Calculate the Empirical Formula of a compound containing 13.43g of Al and 53.18g Cl

Answer 7

O.497 mol Al
1.50 mol Cl

1.50/0.479= 3/1
AlCl3

Question 8

Calculate the Empirical Formula of a compound containing 52.14% C, 13.12% H, and 34.73% O.

Answer 8

4. 35 mol C (2)
5. 2 mol H (6)
6. 17 mol O (1)

C2H6O

Question 9

How to find the Molecular Formula from the Empirical

Answer 9

1) Given the molecular mass, divide by the empirical mass

Question 10

Empirical Formula: CH2O
(empirical mass=molar mass=30)
Molecular mass=180

Answer 10

Ratio: 180/30 = 6

Molecular Formula: 6(CH2O) -> C6H12O6

Question 11

How to find % Yield

Answer 11

Lab (actual)
——————————— X 100%
Theoretical (Calculated)

Question 12

Variables that limit a gas (4)

Answer 12

1) Temperature
2) Volume
3) Moles
4) Pressure

Question 13

What is KMT

Answer 13

Kinetic Molecular Theory

The movement of Molecules/Particles

Question 14

What does KMT involve?

Answer 14

Particle Size
**Volume occupied by a gas is mostly empty space
Particle Motion
**Gas particles move in a straight line in all directions
**CONSTANT RANDOM MOTION
Particle Energy
**No energy is lost by collision of gas particle w/ walls of container

Question 15

NO IDEAL GAS EXISTS

Answer 15

They approach ideal behavior under certain conditions of temperature & pressure

Question 16

What would be the partial (dry) pressure of N2 gas collected over water at 20 degrees C and 720. torr?

Answer 16

P atm= P N2 + P H20

720. torr= P N2 = 17.5 torr
     703 torr= P N2

Question 17

What kind of relationship is Pressure vs. Volume?

Answer 17

Inverse

Question 18

What kind of relationship is Pressure vs. Temperature?

Answer 18

Direct

Question 19

What kind of relationship is Volume vs. Temperature?

Answer 19

Direct

Question 20

When do Mole Ratios=Volume Ratios?

Answer 20

When Pressure and Temperature is the same

Question 21

The equation for Heat

Answer 21

Heat= mass X change in temp X Specific Head

Question 22

Specific Heat

Answer 22

The amount of heat energy required to raise 1 g of a substance 1 degree C

Question 23

Specific heat for water

Answer 23

4.18 J/g degree C

Question 24

A 110.0 g sample of Iron @ 55.5 degrees C raises the temp of 150.0 mL of water from 223.0 degrees C to 25.5 degrees C. Determine the specific heat of the iron.

Answer 24

Heat Gain (H20)= Heat loss (Metal)

(gained by H2O)
Heat =150.0 g X 25 X 4.18
Heat =1600 J

(gained = lost)
1600 J= 110.0g X 30.0 X Cp
Cp= 0.48

Question 25

Enthalpy

Answer 25

The heat content of a system at constant pressure

Question 26

Enthalpy changes for exothermic reactions are always...

Answer 26

Negative

Question 27

Enthalpy changes for endothermic reactions are always..

Answer 27

Positive

Question 28

What do you use when going from solid to melting point?

Answer 28

Heat = mass X temp change X Cs

Question 29

What do you use when going from melting point to liquid?

Answer 29

Heat = mass X H fusion

Question 30

What do you use when going from liquid to boiling point?

Answer 30

Heat = mass X temp change X Cs

Question 31

What do you use when going from boiling point to gas?

Answer 31

Heat= mass X H vaporization

Question 32

What do you use when going from gas to hotter gas?

Answer 32

Heat = mass X temp change X Cs

Question 33

Heat of Fusion

Answer 33

Energy required to change 1g of a solid into a liquid @ its melting point

Question 34

Heat of Vaporization

Answer 34

Energy required to change 1g of liquid into a gas @ its normal boiling point

Question 35

Unique properties of water (5)

Answer 35

1) Changes in Density * *Ice floats on top of water * *Based on temp. * *Hydrogen bonds allow for expansion when freezing 2) Universal Solvent * *Positive end attracts neg ion, neg end attracts pos ion 3) Cohesion & Adhesion 4) High Surface Tension 5) High Heat capacity * *Hydrogen bonds allow for temp. change