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AP Chemistry Unit 6 Thermochemistry

Total questions: 51

Worksheet time: 2hrs 49mins

Name
Class
Date
1.
The heat content of a system at constant pressure is called
a)
entropy
b)
enthalpy
c)
heat
d)
energy
2.
The capacity to do work or transfer heat
a)
temperature
b)
energy
c)
power
d)
enthalpy
3.
The heat required to raise the temperature of WATER 1∘C
a)
calorie
b)
joule
c)
specific heat
d)
energy
4.
Formula for solving specific heat problems
a)
q = mcΔT
b)
H = ΔH x moles
c)
H = ΔH x grams
d)
products - reactants
5.
The following graph shows a(n)
a)
endothermic reaction
b)
exothermic reaction
c)
increase in entropy
d)
decrease in entropy
6.
An endothermic reaction feels _____ to the touch
a)
warm
b)
cool
7.
What type of reaction is shown?
a)
reactants
b)
endothermic
c)
exothermic
d)
products
8.
In an exothermic process the surrounding looses heat. 
a)
True
b)
False
9.
H2 + 2 C + N2 + 270.3 kJ --> 2 HCN
Is this reaction endothermic or exothermic?
a)
Endothermic 
b)
Exothermic
10.
Is the combustion of gasoline endothermic or exothermic?
a)
Endothermic
b)
Exothermic
11.
In a laboratory experiment a student was using Styrofoam cups and foil to reduce the energy lost during an exothermic reaction.  The reaction constantly had a temperature probe in it.  Towards the end of the reaction the student noticed the temperature in the cups was going down (opposite what they thought is should).  The student concluded that the energy was destroyed within the system.  This student's reasoning violates what law?
a)
Law of Conservation of Mass
b)
Law of Enthalpy
c)
First Law of Thermodynamics
d)
Law of Heat Transfer
12.
Which direction does heat flow?
a)
hot to cold
b)
cold to hot
13.
A sample of iron receives 50.J of heat energy that raises the temperature of the iron 25.0°C. If iron has a specific heat of .10 J/g°C, what is the mass of the iron sample?
a)
25g
b)
30g
c)
20g
d)
50g
14.

A liquid with a specific hear of 1.9 J/gC has 4750 J of energy added to it. The temperature changed from 20 degrees C to 30 degrees C, what is the mass of the liquid?

a)

250 cal

b)

2500g

c)

250 g

d)

2500 cal

15.
Refer the the following question:
2N2 + 3H2 --> 2NH3 + 46 kJ
How much energy would be produced if only 1 mol of nitrogen was reacted?
a)
92 kJ
b)
0.143 kJ
c)
23 kJ
d)
15 kJ
16.

Which of the letters (A-D) represents the minimum amount of energy required for the reaction to proceed forward?

a)

A

b)

B

c)

C

d)

D

17.
Which of the letters (A-D) represents the potential energy of the products?
a)
A
b)
B
c)
C
d)
D
18.
(Hess's Law)Calculate the ∆H for the following reaction: 2H2O2 →  2H2O  + 1 O2 
You are given these two equations:
2H2  +  O2 → 2H2O            ∆H  =  -572 kJ
 H2  +  O2  →  H2O2            ∆H  =  -188 kJ 
a)
∆H  =  -948 kJ 
b)
∆H  =  -196 kJ 
c)
∆H  =  -384 kJ 
d)
∆H  =  -188 kJ 
19.
(Hess's Law) Calculate the ∆H for the following reaction:
2CO  +  2NO →  2CO2  +  N2 
You are given these two equations:
 2CO  +  O2 →  2CO2           ∆H  =  -566.0 kJ
 N2  +  O2 →2NO                   ∆H  =  180.6 kJ
a)
∆H  =  -385.4 kJ
b)
∆H  =  -746.6 kJ
c)
∆H  =  385.4 kJ
d)
∆H  =  746.6 kJ
20.
Temperature is a measure of the...
a)
total energy in a substance
b)
total kinetic energy in a substance
c)
average potential energy in a substance
d)
average kinetic energy of molecules in a substance
21.

When thermal energy is added to a substance, the substance's particles move:

a)

More rapidly at an increased distance from each other.

b)

More rapidly with less distance between each other.

c)

More slowly with a greater distance between each other.

d)

More slowly with a reduced distance between each other.

22.
Heat transfer by conduction occurs when...
a)
particles bump into each other
b)
large numbers of atoms move from place to place
c)
atoms give off heat in the form of electromagnetic waves
d)
electromagnetic waves travel from place to place through a vacuum
23.
Heat transfer by convection occurs when...
a)
electrons bump into other electrons
b)
large numbers of atoms move from place to place
c)
atoms give off heat in the form of electromagnetic waves
d)
electromagnetic waves travel from place to place through a vacuum
24.
A substance with a high specific heat:
a)
Is always extremely hot.
b)
Requires a lot of energy to become hot.
c)
Is not heavy.
d)
Does not requires a lot of energy to become hot.
25.
The second  law of thermodynamics states that entropy of a system  tends to ______________. 
a)
increase
b)
decrease
c)
stay constant
d)
fluctuate wildly
26.
The first law of thermodynamics states that energy is
a)
created
b)
destroyed
c)
conserved
d)
created and destroyed
27.
Which law of thermodynamics states that absolute zero cannot be reached?
a)
1st
b)
2nd
c)
3rd
28.
What is "Entropy"?
a)
The tendency of objects to warm up
b)
The tendency of energy to spread out
c)
The tendency of energy to make heat
d)
The tendency of objects to do work
29.

A substance of mass 2.0 kilograms is originally in the solid state. The graph below represents the temperature of the substance as heat is added to it. During which interval is the average kinetic energy of the molecules of the substance unchanged?

a)

BC

b)

CD

c)

AB

d)

AC

30.

Which phase change is exothermic?

a)

H 2O( l) → H 2O( s)

b)

H 2O( l) → H 2O( s)

c)

H 2O( l) → H 2O( g)

d)

H 2O( s) → H 2O( g)

31.
What phase change brings an increase in entropy?
a)
g->s
b)
l->s
c)
l->g
d)
g->l
32.
As NaCl dissolves according to the equation
NaCl(s) → Na+(aq) + Cl-(aq), the entropy of the system 
a)
Increases
b)
Decreases
c)
Remains the same
33.
Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔH for this reaction?
a)
Negative because it is exothermic
b)
Negative because it is endothermic
c)
Positive because it is exothermic
d)
Positive because it is endothermic
34.
When ammonium nitrate dissolves in water, the solution gets cold. Which is true?
a)
Reaction is ENDOTHERMIC with positive ΔH
b)
Reaction is ENDOTHERMIC with -ΔH
c)
Reaction is EXOTHERMIC with a -ΔH
d)
Reaction is EXOTHERMIC with +ΔH
35.
A reaction has a positive ΔH and a positive ΔS. Which of the following is true?
a)
It will be spontaneous at all temperatures.
b)
It will be nonspontaneous at all temperatures.
c)
It will be spontaneous at low temperatures.
d)
It will be spontaneous at high temperatures.
36.
True/False: The rate of a chemical reaction is unrelated to the spontaneity of the reaction.
a)
True
b)
False
37.

At what temperature will a reaction become spontaneous if the change in enthalpy is -192 KJ/mol and the change in entropy is -562 J/mol?

a)

Above 341.6 K

b)

Below 341.6 K

c)

Above .34 K

d)

Below .34 K

38.
Entropy always increases when
a)
enthalpy decreases.
b)
temperature decreases.
c)
temperature increases.
d)
volume increases.
39.

Predict the entropy change, ΔS.

a)

ΔS = +

b)

ΔS = -

c)

ΔS = 0

d)

ΔS = no change

40.
Which 1 g sample will have the highest temperature after the addition of 200 J of energy?
a)
H2O(l)
b)
H2O(g)
c)
Cu
d)
Pb
41.
A 5.00 gram sample of a metal at 85.0 °C comes in contact with 100.0 grams of water at 25.0 °C.  What is the direction of the heat flow and why?
a)
Metal to water, since heat flows from low mass to high mass
b)
Water to metal, since heat flows from high mass to low mass
c)
Metal to water, since heat flows from high temp. to low temp.
d)
Water to metal, since heat flows from low temp. to high temp.
42.
Which of the following would have a nonzero enthalpy of formation?
a)
Fe(s)
b)
Br2(s)
c)
O2(g)
d)
Hg(l)
43.
Which of the following would have a standard enthalpy of formation value of zero?
a)
H2O(l)
b)
H2O(g)
c)
F2(g)
d)
O3(g)
44.
Thermodynamically favorable reactions...
a)
are very fast
b)
occur only with the addition of work
c)
occur without the addition of work
d)
are always exothermic
45.
Thermodynamically favorable reactions tend to go to...
a)
low energy and high entropy
b)
low energy and low entropy
c)
high energy and high entropy
d)
high energy and low entropy
46.
Which of the following possesses the greatest amount of entropy? 
a)
1 mol of Ar(g) at 0.5 atm and 298 K
b)
1 mol of Ar(g) at 0.5 atm and 400 K
c)
2 mol of Ar(g) at 0.5 atm and 400 K 
d)
2 mol of Ar(g) at 1 atm and 400 K
47.
The reaction with the largest increase in entropy is...
a)
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) 
b)
CH4(l) + 2O2(g) → CO2(g) + 2H2O(l) 
c)
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) 
d)
CH4(l) + 2O2(g) → CO2(g) + 2H2O(g)
48.
2N2O5 --> 4NO2 + O2 
             ΔHf
N2O5    11.289 kJ/mol
NO2       33.150 kJ/mol
O2         0 kJ/mol
 ΔHreaction = ?
a)
110.022 kJ
b)
10.572 kJ
c)
121.311 kJ
d)
21.861 kJ
49.

If an equilibrium constant, K>1 , what wll be the sign of the Gibbs Free Energy

a)

Δ G = 0

b)

Δ G < 0

c)

Δ G > 0

50.

For a particular chemical reaction ΔH = 5.5 kJ and ΔS = -25 J/K

Under what temperature conditions is the reaction thermodynamically favored?

a)

When T < -220 K

b)

When T < 220 K

c)

The reaction is spontaneous at all temperatures.

d)

The reaction is not spontaneous at any temperatures.

51.

The Ksp for a very insoluble salt is 4.2 x 10-47 at 298 K. What is ΔG° for the dissolution of the salt in water?

a)

-265 kJ/molrxn

b)

+265 kJ/molrxn

c)

-115 kJ/molrxn

d)

+115 kJ/molrxn

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