Practice Midterm 1
2O3(g) → 3O2(g)
O2(g) → 2O(g)
NO(g) + O3(g) → NO2(g) + O2(g)
1. Given the following:
Ch 9, 10
ΔH = -427 kJ
ΔH = 495 kJ
ΔH = -199 kJ
Calculate ΔH for the reaction: NO(g) + O(g) → NO2(g)
2. Indicate whether the following quantities (w, q, ΔE, ΔH, ΔS, ΔG) are positive, negative or
zero for the following isothermal processes.
a. Ne(g) is compressed from 2L to 1L
b. an ideal gas expands from 250 mL to 300 mL against a constant external pressure of 1 atm
c. Argon gas expands into an evacuated container (free expansion)
d. an ideal gas is expanded reversibly from 1L to 2L
3. Calculate ΔE, ΔH, q and w for the following:
a. heating 2.0 moles of neon gas from 75 ºC to 85 ºC in a rigid container.
b. cooling a balloon containg 10.0 g of nitrous oxide (N2O) from 100 ºC to 25 ºC at 1.00 atm
constant pressure. (Cp = 38. 7 J/mol K)
c. expanding 1 mole of argon isothermally and reversibly from 1 L to 5 L.
4. The enthalpy change for the conversion of diamond into graphite is -1.9 kJ/mol. If the same
amounts of diamond and graphite are burned, which will give off more heat?
5. How much heat is required to raise the temperature of 10.0 g of a metal from 25.0 to 60.0 °C.
The specific heat capacity of the metal is 0.18 J/g°C.
6. Why are the values of Cp and Cv greater for polyatomic gases than monatomic gases?
7. Suppose 3.00 g of glucose (C6H12O6) are placed in a constant volume calorimeter which is
filled with oxygen gas. The calorimeter contains 12.00 g of water at an initial temperature of 19
°C. The glucose is combusted and the temperature of the calorimeter and water rises to 25.5 °C.
Calculate the heat evolved for the combustion of 1 mole of glucose and ∆E for the reaction.
(Ccal = 2.21 kJ/°C, Cwater = 4.18 J/g °C)
8. A 25.0 g piece of unknown metal was heated in a bath of boiling water and then transferred to
a calorimeter containing 150 mL of water at 24 ºC. The temperature at equilibrium was found to
be 27.2 °C. Calculate the specific heat capacity of the unknown metal. (Ccal = 25.0 J/ºC and
Cwater = 4.18 J/g ºC)
9. Consider the reaction
2 HCl + Ba(OH)2 → BaCl2 + 2H2O
ΔH = -118 kJ
Assume you mix 100.0 mL of 0.200 M HCl and 200.0 mL of 0.100 M Ba(OH)2. If both solutions
are initially at 25 ºC, what is the final temperature of the mixture?(Cwater = 4.18 J/g ºC)
10. Predict the sign of ΔH, q and w for the following endothermic reaction occurring at 25 ºC
and constant pressure.
2NH3(g) → N2(g) + 3H2(g)
11. Consider the freezing of liquid water at -10 °C. For this process what are the signs of ∆H, ∆S
and ∆G?
12. Circle which has the greatest entropy
a. 1 mol Ar or 2 mol Ar
b. NO(g) or C2H6(g)
c. H2O(l) or H2O (s)
d. 1 mol He at 50 ºC and 1 atm or 1 mol He at 25 ºC and 1 atm
e. 1 mol He (g) in 1L or 1 mol He(g) in 2 L
13. For the following reactions state whether there will be an increase, decrease or no change in
entropy.
a. freezing water
b. decomposition of solid magnesium carbonate
c. formation of NH3 gas
d. precipitation of AgCl
14. At constant pressure, the following reaction is exothermic: 2NO2(g)  N2O4(g)
The reaction as written is: (choose the correct answer)
a. always spontaneous
b. spontaneous at low temperatures
c. spontaneous at high temperatures
d. never spontaneous
15. Write the formation reaction for tetrahydrocannibinol (C21H30O2).
16. Consider the reaction at 25 °C and 1 atm.
2POCl3(g) → 2PCl3(g) + O2(g) ΔGº = 463 kJ
a. is this reaction spontaneous?
b. if ΔSº = 179 J/K, at what temperature is this reaction spontaneous?
17. Given the following, calculate ΔGº for the reaction at 25 ºC.
P4O10(s) + 6H2O(l) → 4H3PO4(s)
H2O (l)
H3PO4(s)
P4O10(s)
ΔHfº
-286 kJ/mol
-1279 kJ/mol
-2984 kJ/mol
Sº
70 J/K mol
110 J/K mol
229 J/K mol
18. When 1.00 g of a liquid freezes at the temperature of its freezing point, its enthalpy decreases
by 0.126 kJ and its entropy decreases by 0.452 J/degree. What is the freezing point temperature
for the liquid?
19. The value of ΔGº for the reaction 2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(l) is -5490 kJ.
Given the following data, calculate the standard free energy of formation for C4H10(g).
ΔGfº (CO2(g)) = -394 kJ/mol, ΔGfº (H2O(l)) = -237 kJ/mol
20. Consider the dissociation of the weak acid HOCl in water. ΔGº for this process is 42.5
kJ/mole. If 1.00 mole of HOCl is dissolved in 1.00 L water at 25 ºC, what is the concentration of
HOCl, H+, and OCl- at equilibrium?
21. At 25 ºC, Kp= 98.4 for the reaction 2NO(g) + Br2(g) → 2NOBr(g). Calculate ΔG at 25 ºC
when PNO = 0.2 atm, PBr2= 0.5 atm and PNOBr = 0.3 atm.
22. At 700 ºC the value of Kp for a particular reaction is 1.5 and ΔHº = -818.3 kJ/mol. What is
the equilibrium constant at 1000 ºC?