Ch. 10 & 14  thermodynamics            test      60 points                                 chem

 

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer. 

 

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

 

                                                                                                Signature:  ___________________

 

1.  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]

 


2.  In regards to dissolving solid ammonium nitrate in water,  [20 points]

 

a.  what is the chemical equation to describe this process ?

 

b.  what is the mathematical / thermodynamic equation to determine Δ H of this process ?

 

c.  what is the Δ H of this process based on the following experimental data:  dissolving 3.0 g of solid ammonium nitrate in 50. mL water at 21 °C caused its temperature to change to 15 °C. 

d.  determine  based on the preceding information. 

 

 

3.  fill-in the below table  [10 points]

 

Reaction happens ?  Y / N

Δ G  (+ / -); describe  any temperature dependence

Δ H

Δ S

 

 

 

 

 

+

 

+

 

 

 

 

 

-

 

-

 

 

 

 

 

-

 

+

 

 

 

 

 

+

 

-

 

 

 

4.  What is Δ S of the following reactions (i.e. positive or negative); justify / rationalize your answer.  [10 points]

 

a.   C2H5OH (g)  +  O2 (g)  à  CO2 (g)   +  H2O (g)

 

 

b.  dissolve solid ammonium nitrate in water