Ch.  14 & 10 thermodynamics                         test                                          75 points                                                               chemistry
Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of significant figures in your answer. 


1.  Based on the following information in regards to ethanol

∆Hfusion = 5.02 kJ / mol                                                freezing point = -114 °C
∆Hvaporization = 38.56 kJ / mol                                        boiling point = 78 °C
specific heat
liquid = 2.3 J / g K
solid =  0.97 J / g K
gas =  0.86 J / g K

determine the amount of heat consumed by 10.0 grams of ethanol  __ .  [10 points; weekly quiz problem]

a. at -25 °C to become ethanol at 25 °C

b. at its melting point, to melt all of the solid ethanol without a change in its temperature

2. A 35 g (hypothetical ?) metal was put into a 95 ºC water bath for about 10 minutes (to equilibrate its temperature), then put into 65 mL of water at 21 ºC; the temperature increased to 23 ºC.  Based on the preceding information, what is the specific heat of the metal ?  [10 points; weekly quiz problem]

3. What is the “final” temperature after mixing 100. mL water at 90. ºC  and 50. mL water at 10. ºC ?  [10 points; homework problem]

4. 25 g of ammonium nitrate, NH4NO3, was dissolved in 60.0 g of water, where the temperature changed from 22.0 ºC to 16.9 ºC.  What is the change in enthalpy, in kJ / mole, to dissolve NH4NO3 in water ?   [10 points; homework problem]

5. Given

2 O3 → 3 O2                           ΔH1 = - 427 kJ
O2  →  2 O                               ΔH2 = 495 kJ
NO + O3  →  NO2  +  O2          ΔH3 = - 199 kJ

Determine  ΔH for the reaction:  NO  +  O  →  NO2.  [10 points; homework problem]

6.  What is ΔS in the following ___; positive, negative, zero, or ambiguous; justify / rationalize your answer.  [10 points]

a.  Dissolving solid sodium chloride in water

b.  N2(g)  +  H2(g)  →  NH3(g)

c.  Freezing a liquid

.d.  Mixing aqueous solutions of silver nitrate and sodium chloride  [hint:  it’s a double replacement reaction & apply the solubility rules]

7. What is ΔH, ΔS, and ΔG, i.e. positive, negative, zero, or ambiguous, in the following: __; justify / rationalize your answer and if it depends on the temperature, then clearly state it in your answer.  [15 points]

a. Boiling water

b. Freezing water

c.  Combustion of ethane, C2H6  [assume that all chemicals in the reaction is a gas]