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WorksheetsThermochemistry!
Total questions: 28
Worksheet time: 1hrs 25mins
Name
Class
Date
1.
What is the latent heat of fusion of lead (in joules per gram), if 6.30 kilojoules of heat are required to convert 255 grams of solid lead at its melting point into a liquid?
a)
.025
b)
1.61
c)
24.7
d)
40.5
2.
In an exothermic process, the surroundings are are gaining energy.
a)
True
b)
False
3.
Is the combustion of gasoline endothermic or exothermic?
a)
Endothermic
b)
Exothermic
4.
For the formula:
Q= m c ∆T
The units for specific heat are:
Q= m c ∆T
The units for specific heat are:
a)
g /J C
b)
°C/g J
c)
kJ/g
d)
J/g°C
5.
The specific heat is the amount of energy needed to raise the temperature one degree Celsius of a substance.
a)
True
b)
False
6.
As a reaction is taken place, the student notices that the temperature has dropped. This indicates that the system has increased in energy. What type of process is this?
a)
Endothermic
b)
Exothermic
7.
Using the heat equation, what would the formula look like if we were solving for change in temperature?
a)
Q m=∆T c
b)
Q/mc= ∆T
c)
Qm/c=∆T
d)
mcQ=∆T
8.
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
9.
Refer the the following question:
2N2 + 3H2 --> 2NH3 + 46 kJ
How much energy would be produced if only 1 mol of nitrogen was reacted?
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
10.
A reaction is performed in a beaker with a temperature probe recording the temperature changes of the reaction. If the temperature began at 15.0 degrees Celsius and ended at 27.5 degrees Celsius. If the reaction is our system, is the system endothermic or exothermic?
a)
Exothermic
b)
Endothermic
11.
Do reactants in an endothermic reaction have a higher or lower energy than the products?
a)
Higher
b)
Lower
12.
H2 + Cl2 --> 2 HCl + 1845 kJ
Is this reaction endothermic or exothermic?
Is this reaction endothermic or exothermic?
a)
Endothermic
b)
Exothermic
13.
Calorimetry Question:
A piece of metal with a mass of 32.8 g is heated to 100.5°C and dropped into 138.2 g of water at 20.0°C. The final temperature of the system is 30.2°C. What is the specific heat capacity of the metal? (show your work)
A piece of metal with a mass of 32.8 g is heated to 100.5°C and dropped into 138.2 g of water at 20.0°C. The final temperature of the system is 30.2°C. What is the specific heat capacity of the metal? (show your work)
a)
2.56 J/g°C
b)
0.391 J/g°C
c)
5.29 J/g°C
d)
3.50 J/g°C
14.
How much energy does it take to freeze 39.2 g of liquid benzene? (ΔHfus = 126 J/g, ΔHvap = 394 J/g) (Show your work)
a)
4940 J
b)
-4940 J
c)
15400 J
d)
-15400 J
15.
What letter represents boiling?
a)
B
b)
C
c)
D
d)
E
16.
What letter represents a liquid being heated?
a)
A
b)
B
c)
C
d)
D
17.
The amount of heat it takes to raise one gram of water by one degree celsius
a)
joule
b)
calorie
c)
kilocalorie
d)
specific heat
18.
What type of reaction is pictured behind?
a)
endothermic
b)
exothermic
19.
What type of reaction is the following?
6 CO2 +6 H2O --> C6H12O6 + 6 O2 + 114 kcal
6 CO2 +6 H2O --> C6H12O6 + 6 O2 + 114 kcal
a)
exothermic
b)
endothermic
20.
What would be the effect on the particles if more heat is supplied to the system?
a)
They would slow down
b)
They would stop moving
c)
They would speed up
d)
There would be no effect
21.
The __________ law of thermodynamics states that entropy is always increasing.
a)
first
b)
second
c)
third
d)
zeroth
22.
ΔH value in an endothermic reaction is a positive number.
a)
True
b)
False
23.
Which phase of matter has the greatest motion and least orderly arrangement?
a)
solid
b)
liquid
c)
gas
24.
The equation that relates enthalpy, temperature and entropy is
a)
Hess's Law
b)
Second Law of Thermodynamics
c)
Gibbs Free Energy
d)
Calorimetry
25.
For which of these processes is the value of ΔH expected to be positive?
1. The temperature increases when calcium chloride dissolves in water.
2. Steam condenses to liquid water
3. Water boils
4. Dry ice sublimates
1. The temperature increases when calcium chloride dissolves in water.
2. Steam condenses to liquid water
3. Water boils
4. Dry ice sublimates
a)
4 only
b)
1 only
c)
3 and 4 only
d)
2 and 3 only
26.
The formation ½ A2 + 2 B2 + C --> CAB4 has an enthalpy of formation of -104 kJ and a change in entropy of -.0608 kJ/K at 303 K. What is the free energy and spontaneity of the reaction?
a)
-122 kJ, spontaneous
b)
-18.3 kJ, not spontaneous
c)
+18.3 kJ, spontaneous
d)
+122 kJ, not spontaneous
27.
what is the disorder of the system known as?
a)
efficiency
b)
fast moving particles
c)
entropy
28.
The free energy change, DG, must be negative when
(Note D=delta)
(Note D=delta)
a)
DH is positive and DS is positive.
b)
DH is negative and DS is positive.
c)
DH is positive and DS is negative.
d)
DH is negative and DS is negative.
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