Ch. 5, 8.9, 11.4, & 19 thermodynamics test [85 points] AP Chemistry

For problems involving calculations, show your work in an organized manner, include any relevant equation / formula, proper units in your work / answer, and the proper number of significant figures in your answer.

1. old topic: phase diagram of water. [15 points]

a. Sketch its phase diagram and label the regions in the diagram corresponding to liquid, gas, and solid.

b. rationalize the slope (i.e. positive versus negative) of the border between the solid and liquid phases.

 

2. Based on the following information in regards to ethanol

∆H fusion = 5.02 kJ / mol freezing point = -114 °C

∆H vaporization = 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 at -20 °C to become ethanol at 90.0 °C. [15 points]

3. Determine Δ Hf (NO3 -) based on the following (hypothetical) experimental results. The initial and final temperature of water was 21.0 and 15.0 °C, respectively after dissolving 2.0 grams of solid ammonium nitrate in 50.0 mL of water. The specific heat of water is 4.18 J / g K. [15 points]

 

a. write the chemical equation that describes this reaction.

b. Based upon the above experimental data, determine ∆H reaction.

c. Based upon the above experimental data, determine Δ Hf (NO3 -).

 

4. In regards to the reaction: NaOH (s) --> Na +(aq) + OH - (aq) [20 points]

a. what factors affect the sign of ∆S reaction ? rationalize your answer.

b. calculate ∆S reaction

c. rationalize / justify the sign of ∆S reaction

d. based on thermodynamics, is the above reaction spontaneous ? Justify your answer.

 

5. In regards to the reaction: C 5H 12 + O 2 <--> CO 2 + H 2O    [20 points]

a. write the balanced chemical equation for this reaction.

b. How many moles of n-pentane is there in 5.0 grams of n-pentane ?

c. Determine ∆H reaction ?

d. How much heat would be generated by the combustion of 5.0 grams of n-pentane ?