Ch. 10 & 14  thermodynamics            test      60 points                                             honors 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.

 

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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 ?  [20 points]

 

2.  Determine  based on the following hypothetical experimental results:  dissolving 3.0 g of solid ammonium nitrate in 50. mL water at 21 °C caused its temperature to change to 15 °C.  [15 points]

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

 

Reaction happens ?  Y / N

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

Δ H

Δ S

 

 

 

 

 

+

 

+

 

 

 

 

 

-

 

-

 

 

 

 

 

-

 

+

 

 

 

 

 

+

 

-

4.   Use the thermochemical equations shown below to determine the enthalpy for the final reaction.  [15 points]


(1)  C3H8(g) + 5O2{g}  à  3CO2 + 4 H2O(l)                         Δ H1 = -3108 kJ


(2)  CO2  à  C(graphite) + O2                                    Δ H2 = 552 kJ

(3)  C3H8(g)  à  3 C(graphite) + 4H2(g)                     Δ H3 = 146 kJ

H2(g) + 1/2O2(g)  à H2O(l)                                        Δ H = ?