Practice Questions
|
Statement I |
| Statement
II |
| 1. |
The reaction shown above is exothermic. |
BECAUSE | The total enthalpy
of the products in this reaction is less than that of the reactants. |
|
|
| 2. |
Use
the bond energies given below to estimate the enthalpy, DH,
for the following reaction: |
|
|
| (A) |
DH = -800 kJ |
| (B) |
DH = -680 kJ |
| (C) |
DH = -150 kJ |
| (D) |
DH = +150 kJ |
| (E) |
DH = +200 kJ |
|
|
|
| 3. |
Each
of two solutions are mixed separately, and both solutions are found
to be the same temperature. The two solutions are mixed, and a thermometer
shows that the mixture’s temperature has decreased in temperature.
Which of the following statements is true? |
| (A) |
The chemical reaction is exothermic. |
| (B) |
The chemical reaction is absorbing energy. |
| (C) |
The chemical reaction is releasing energy. |
| (D) |
The energy released could be found by multiplying
the temperatures together. |
| (E) |
The energy absorbed by the solution is equal
to the difference in temperature of the solutions. |
|
|
| 4. |
Consider
the reaction below. When a 45.00 gram sample of ethanol is burned
with excess oxygen, about how much energy is released as heat? |
|
C2H5OH(l) +
3O2(g) 2CO2(g) +
3H2O(l)
∆H = -1.40 103 kJ |
| (A) |
0.995 kJ |
| (B) |
5.1 102 kJ |
| (C) |
1.40 103 kJ |
| (D) |
2.80 103 kJ |
| (E) |
5000 kJ |
|
|
| 5. |
In neutralizing
500 mL of 1.0 M HCl with 500 mL of 1.0 M NaOH, the temperature of
the solution rises 5.0ºC. Given that the density of the solution
is 1.0 g/mL and the specific heat of the solution is 4.184 J/g ºC,
calculate the approximate energy released from this experiment. |
| (A) |
20 J |
| (B) |
1000 J |
| (C) |
4200 J |
| (D) |
2.1 104 J |
| (E) |
1.0 104 kJ |
|
|
| 6. |
Based on
the relationship of entropy to the degree of disorder of a system,
which response includes all the occurrences listed that represent
a decrease in entropy? |
|
I. The freezing of water
II. The vaporization of water
III. Sublimation (vaporization) of dry ice, solid CO2
IV. The extraction of Mg and pure water from seawater
|
| (A) |
I and II |
| (B) |
II and IV |
| (C) |
I and IV |
| (D) |
III |
| (E) |
II and III |
|
|
| 7. |
Spontaneous
reactions are driven by |
| (A) |
Low enthalpy values and high entropy values |
| (B) |
Low enthalpy values and low entropy values |
| (C) |
High enthalpy values and low entropy values |
| (D) |
High enthalpy values and high entropy values |
| (E) |
High temperatures and low pressures |
|
|
|
| 8. |
If
an exothermic process is spontaneous, which of the following statements
must be true? |
| (A) |
DG must be positive. |
| (B) |
DS must be positive. |
| (C) |
DS must be negative. |
| (D) |
The temperature must be over 500K. |
| (E) |
DG must be negative. |
|
|
| 9. |
Consider
the following hypothetical reaction (at 375K). The standard free
energies in kJ/mol are given below each substance in parentheses.What
is the value of the Gibb’s free energy for the reaction at this
temperature? Is the reaction spontaneous? |
|
|
| (A) |
-220; yes |
| (B) |
-180; no |
| (C) |
-160; yes |
| (D) |
+180; no |
| (E) |
-160; no |
|
|
| 10. |
Which of
the following events is least likely to occur with
an increase in temperature for the reaction given? (With  H = -45.9 kJ/mol.) |
|
|
| (A) |
The gas particles will move more quickly. |
| (B) |
The reaction will produce more ammonia in a shorter time. |
| (C) |
The reaction will reverse and ammonia will decompose. |
| (D) |
The entropy of the system will increase. |
| (E) |
The equilibrium constant will become smaller. |
|
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