Ch. 10 & 14.2-14.3  thermodynamics test                   75 points                                                          chem

Show your work in an organized manner, including equation / formula, proper conversion factor(s), equation or formula, and units in your work / answer and the proper number of significant figures in your answer.

1. In the below reactions  ____;  ΔS > 0 ? ΔS < 0 ?  ΔS ≈ 0 ?  ΔS is ambiguous ?  justify / rationalize your answer.   [15 points; mostly weekly quiz question]

a.  H2(g)  +   Cl2(g)  →  HCl(g)

b. N2(g)  +  H2(g)  →  NH3(g)

c. dissolve solid potassium hydroxide in water

2. Based on thermodynamics, what is the boiling point of water ?  hints:  ΔS = 123 J / K  and H2O(l)  →  H2O(g) is a chemical equation that describes it.   [10 points; weekly quiz question]

3. Based on the following information for ethanol (C2H5OH), 

  Melting point = -114 °C         ΔHfusion = 5.02 kJ / mol                        c (solid) = 0.97 J / (g K)
Boiling point = 78 °C             ΔHvaporization = 38.56 kJ / mol    c (liquid) = 2.3 J / (g K)                                                                                                                                                           c (gas) =  1.67 J / (g K)

what is the amount of heat needed for ethanol at -25 °C to goto ethanol at 85 °C ?  [hint:  sketch the heating curve & label it;  20 points; past test question]

4. What is the change in temperature due to the addition of 1.5 grams of potassium hydroxide in 75 mL of water ?  [15 points; past test question]

5.  If dissolving 3.0 g of solid ammonium nitrate in 50. mL water at 21 °C caused its temperature to change to 15 °C, determine .   [15 points; past test question]