Name:  _____________________                              date:  __________________               period: _______

Ch. 14.2  heating curve & ch.  10 thermodynamics     70 points (4 ec)                                      chemistry

In problems involving any calculation, 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. What is ΔS, i.e. positive, negative, zero, or ambiguous;  justify / rationalize your answer.  [9 points]

a.  Freezing water

b.  H2(g)  +  O2(g)  -->  H2O(g)

c.  Dissolve solid sodium hydroxide in water

2. Estimate the boiling point of water based on thermodynamics.  [10 points; hint:  H2O(l)  -->  H2O(g); ΔS = 119 J / (mole K))

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  __ .  [15 points]

a. sketch and label the axis of a heating curve for ethanol, including the temperature corresponding to its freezing point and its boiling point

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

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

4.  Based on
NO  +  O3  --> NO2  +  O2                    ΔH1 = -200 kJ

O3 --> (3/2) O2                              ΔH2 = -140 kJ
O2  -->  2 O                               ΔH3 =  495 kJ


find      NO  +  O  -->  NO2                               ΔH = ?    [10 points]

5. How much heat would be generated in the combustion of 5.0 g of butane, C4H10 ?  Assume all chemicals in the reaction are gases.  [20 points]

6.  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]