Ch. 10 & 14.2-14.3 thermodynamics test 95 points honors 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. Given:

find [10 points; weekly quiz question]

ΔH = ?

2. What is ΔS in the below situations (i.e. ΔS > 0; ΔS < 0; ΔS ≌ 0; ambiguous); justify / rationalize your response. [15 points; last year’s test question]

a. Mix aqueous solutions of silver nitrate and sodium chloride

b. Dissolve magnesium chloride in water

c. Melting of ice

3. What is the “final” temperature of water after dissolving 2**.**0 grams of solid sodium hydroxide in 75 mL of water at an initial temperature of 21 ºC ? [20 points; weekly quiz problem]

4. Calculate the number of grams of water, where the addition of 50**.**0 g of copper at 100**.** °C would change the temperature of water by 5.0 °C; assume that the initial temperature of the water is 20**.**0 °C; specific heat of copper is 0.38 J / (g K). [15 points; prelab problem]

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

6. Ethanol, C2H5OH, melts at – 114 °C and boils at 78 °C. The enthalpy of fusion is 5.02 kJ / mol and its enthalpy of vaporization is 38.56 kJ / mol. The specific heats of solid, liquid, and gas is 0.97 J / g-°C, 2.3 J /g-°C, and 1.88 J / g-°C, respectively. How much heat to convert 50**.**0 g of ethanol at -150 °C to vapor phase at 78 °C ? [25 points; 2 year ago test question]