WorksheetsEntropy Enthalpy Spontaneous Reactions
Total questions: 20
Worksheet time: 22mins
Name
Class
Date
1.
The __________ law of thermodynamics states that entropy is always increasing.
a)
first
b)
second
c)
third
d)
zeroth
2.
Temperature is a measure of average _________ energy of individual atoms.
a)
heat
b)
potential
c)
mechanical
d)
kinetic
3.
ΔH value in an endothermic reaction is a positive number.
a)
True
b)
False
4.
Which phase of matter has the greatest motion and least orderly arrangement?
a)
solid
b)
liquid
c)
gas
5.
The equation that relates enthalpy, temperature and entropy is
a)
Hess's Law
b)
Second Law of Thermodynamics
c)
Gibbs Free Energy
d)
Calorimetry
6.
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
7.
6. The formation ½ A2 + 2 B2 + C --> CAB4 has an enthalpy of formation of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?
a)
-85.6 kJ, spontaneous
b)
-18.3 kJ, not spontaneous
c)
+18.3 kJ, spontaneous
d)
+85.6 kJ, not spontaneous
8.
When a liquid boils what are the signs for Δ H and Δ S ? (Think about H2O as an example!)
a)
Δ H = + Δ S = +
b)
Δ H = - Δ S = -
c)
Δ H = + Δ S = -
d)
Δ H = - Δ S = +
9.
Spontaneity is determined by....
a)
enthalpy only
b)
entropy only
c)
enthalpy and entropy
d)
enthalpy, entropy, and temperature
10.
Solid magnesium dissolves in a solution of hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔG for this reaction?
a)
Negative because it is spontaneous
b)
Negative because it is nonspontaneous
c)
Positive because it is spontaneous
d)
Positive because it is nonspontaneous
11.
What signs of Δ H and Δ S will always yield a reaction that is spontaneous ? (Think of the equation for ΔG°!!)
a)
Δ H = + Δ S = +
b)
Δ H = - Δ S = -
c)
Δ H = - Δ S = +
d)
Δ H = + Δ S = --
12.
Predict the signs of Δ H , Δ S and Δ G for the reaction:
H2 (g) → 2 H(g)
H2 (g) → 2 H(g)
a)
Δ H= - , Δ S = + and Δ G = - (all temps)
b)
Δ H= + , Δ S = + and Δ G = - (At all temps)
c)
Δ H= + , Δ S = + and Δ G = - (At low temps)
d)
Δ H= + , Δ S = + and Δ G = - (At high temps)
13.
Calculate ΔG° for a reaction for which ΔH° = 24.6 kJ and ΔS° = 132 J/K at 298 K. Is the reaction spontaneous at these conditions? (LOOK AT UNITS!!!)
a)
Yes because ΔG° = -39.3 kJ
b)
Yes because ΔG° = -14.7 kJ
c)
No because ΔG° = 39.4 kJ
d)
No because ΔG° = 63.9 kJ
14.
Calculate ΔG° at 298 K for the combustion of methane.
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
CH4 (g): -50.8 kJ/mol
O2 (g): 0 kJ/mol
CO2 (g): -394.4 kJ/mol
H2O (g): -228.57 kJ/mol
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
CH4 (g): -50.8 kJ/mol
O2 (g): 0 kJ/mol
CO2 (g): -394.4 kJ/mol
H2O (g): -228.57 kJ/mol
a)
-572 kJ
b)
572 kJ
c)
-801 kJ
d)
801 kJ
15.
An equilibrium constant with a large magnitude indicates…
a)
A very fast reaction
b)
Higher concentration of products at equilibrium
c)
Higher concentration of reactants at equilibrium
d)
Nothing, without considering the stoichiometry of the reaction
16.
The equation for Gibbs at NONSTANDARD conditions (ΔG) is....
a)
ΔG = ΔG° + RTlnQ
b)
Don't click this.
c)
Seriously, don't click this.
d)
I can't believe you clicked this.
17.
If ΔG becomes more negative compared to ΔG°.....
a)
that means the reaction is less spontaneous
b)
that means the reaction is more spontaneous
18.
For the reaction below, an increase in the concentration of N2.... [Hint: Think LeChatelier's principle.]
N2 (g) + 3 H2 (g) → 2 NH3
a)
increases ΔG (less spontaneous)
b)
decreases ΔG (more spontaneous)
c)
increases ΔG (more spontaneous)
d)
decreases ΔG (less spontaneous)
19.
If the equilibrium constant for a reaction is LARGE, this means......
a)
ΔG° is very negative and spontaneous.
b)
ΔG° is very negative and nonspontaneous.
c)
ΔG° is very positive and spontaneous.
d)
ΔG° is very positive and nonspontaneous.
20.
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? (R = 8.314 J/(mol⋅K))
a)
-265 kJ/molrxn
b)
+265 kJ/molrxn
c)
-115 kJ/molrxn
d)
+115 kJ/molrxn
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