Chapter 11

Question 1

What do state functions depend on?

Answer 1

The initial and final states of the system - does not depend on how it got there!

Question 2

_____ and _____ are not considered state functions.

Answer 2

work and heat

Question 3

What are the laws of thermodynamics?

Answer 3

1) conservation of energy
2) Entropy is always increasing
3) A perfect crystal has an entropy that is close to, or approaches 0

Question 4

Identify whether the following consumes heat or releases it, and whether it is stable or unstable:

Exothermic
Endothermic

Answer 4

Exothermic - releases heat, stable

Endothermic - consumes heat, less stable

Question 5

The enthalpy of formation for atoms in their standard state = ______

Answer 5

0

Question 6

Which atoms exist as gases in their standard states?

Answer 6

N, O, F, Cl, the noble gases, and H

Question 7

Which atoms exist as liquids in their standard states?

Answer 7

Hg and Br

Question 8

Define what it means if q > 0, and if q < 0

Answer 8

q > 0 = surroundings are transferring heat into the system (endothermic)

q < 0 = the system is giving off heat to its surroundings (exothermic)

Question 9

In the formula w = -PtV, what does it mean if w is positive? How about if it’s negative?

*t = delta sign

Answer 9

(+) w = surroundings are doing work on the system; compression

(-) w = system is doing work on the surroundings

Question 10

On a heat curves, inclines indicate _____, while plateaus indicate _____

Answer 10

phase, phase change

Question 11

Define the meaning of the following:

K > 1

K < 1

Answer 11

K > 1 = products favored

K < 1 = reactants favored

Question 12

T/F? Entropy increases with increasing molecular complexity?

Answer 12

TRUE

Question 13

5.0 g of food was combusted in a bomb calorimeter. The temperature increased from 25 oC to 50 oC. How much energy can be obtained per gram of the food? The heat capacity of the bomb calorimeter is 10.0 kJ/oC.

  A. 100 kJ
  B. 50 kJ
  C. 500 kJ
  D. 25 kJ
  E. 20 kJ

Answer 13

B

-10 x 25 = -250 / 5 g = 50

Question 14

How many of the following transformations has ΔS < 0?

I. CO2(g, 25 oC, 1 atm) → CO2 (g, 25 oC, 2 atm)

II. CO2(s, –78.5 oC, 1 atm) → CO2(g, –78.5 oC, 1 atm)

III. CO2(s, –100 oC, 1 atm) → CO2(s, –200 oC, 1 atm)

IV. CO2(l, –23 oC, 6 atm) → CO2(g, –23 oC, 6 atm)

V. CO2(g, 30 oC, 1 atm) → CO2(g, 40 oC, 1 atm)

  A. one
  B. two
  C. three
  D. four
  E. five

Answer 14

B

Explanation - entropy will DECREASE with a decrease in temperature and pressure

Question 15

Arrange the following in order of increasing final temperature when the same amount of heat is added to 1 g of each substance at the same initial temperature, assuming no heat is lost during the process.

Substance     Specific Heat Capacity, J/g oC 
  Mg                       1.020 
  Al                         0.900 
  Fe                        0.444 
  Ag                        0.240

  A. I < II < III < IV
  B. II < I < IV < III
  C. IV < III < II < I
  D. I < III < II < IV
  E. III < IV < I < II

Answer 15

A

q = mCΔT

We see from this equation that for a given amount of heat (q), temperature change (ΔT) increases as heat capacity (C) decreases.

Question 16

Enthalpy (exothermic or endothermic) of a reaction can be determined by using what formula?

Answer 16

Bonds broken - bonds formed

aka products - reactants

Question 17

Arrange the following in order of increasing ΔGo (most negative to least negative) at 298 K.

I. N2(g) + 3 H2(g) → 2 NH3(g) (K = 1.45 x 10–5)
II. H2(g) + I2(g) → 2 HI(g) (K = 50.5)
III. PCl5(g) → PCl3(g) + Cl2(g) (K = 0.50)

  A. I < III < II
  B. II < III < I
  C. III < I < II
  D. I < II < III
  E. III < II < I

Answer 17

B

the larger the value of K, the smaller (more negative) the value of ΔGo.
Also note that for K > 1, ln (K) > 0, so ΔGo is negative, which implies a spontaneous (product-favored) reaction