Ch. 10 & 14 thermodynamics              test                               85 points                                               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. In regards to ethanol, C2H5OH,

Specific heat; liquid

2.3 J / (g ºC)

Specific heat; gas

1.5 J / (g ºC)

Specific heat; solid

0.97 J / (g ºC)

Heat of fusion

4.9 kJ / mole

Heat of vaporization

35 kJ / mole

Boiling point

78 ºC

Melting point

-114 ºC

How much heat is needed for 15.0 g of ethanol at -135 ºC to be at 85 ºC ?  [30 points]

2.  What is ΔS for ___; justify / rationalize your answer.  [15 points]

a. NH3(g)  →  N2(g)  +  H2(g)

b. Dissolve solid potassium chloride in water

c. Freeze rubbing alcohol

3. What is ΔH for the reaction:  5.0 g CH4(g)  +  excess O2(g)  →  CO2(g)  +  H2O(g).  [15 points]


4. Based on thermodynamics, estimate the boiling point of benzene, C6H6, where ΔS to boil benzene is 96 J / K.  [10 points]

5. What is the final temperature of dissolving 5.0 g solid sodium hydroxide in 125 mL water at 19 ºC ?  [15 points; hint:  based on notes in prelab problems; weekly quiz question]