Unit 8 Review worksheet

1) Propane, C3H8, is combusted in oxygen to create carbon dioxide and water vapor.  What is the ΔHrx for this reaction?-2

2) What is the molar heat of combustion for propane, C3H8, in problem #1?

• same

• 2x as much

• 1/2 as much

• who cares

1. 3) What symbol is used to represent Free Energy?

• ΔH

• ΔI

• ΔJ

• ΔG

4) What is Entropy in a couple of words?

1. 5) What type of reactions would tend to be spontaneous?  Discuss using Enthalpy and Entropy.

1. 6) Please complete the following using Hess’s Law.  Show all your work below:

7) A student dissolves 15.0 g of NH4Cl in 150.0 g of water originally at 20oC.  The water cools to 17oC.  What is ΔH (in kJ/mol) for the dissolution of NH4Cl?   Write a balanced equation for this dissolution as part of your answer. {Molar Mass (g/mol):  N = 14.0,      H = 1.00, Cl = 35.5}

8) List four factors that influence the rate of a chemical reaction. Then describe how the collision theory helps to explain each factor.

9)

1. The ΔS for a reaction is -3.0 J/(mol·K) at 50°C. Calculate the ΔG for the reaction when ΔH = –500.0 J/mol and determine whether it will occur spontaneously at this temperature.  Explain your answer in addition to showing work.  If not spontaneous, when could it be?

10) Analyze the thermochemical equation below, then predict whether the reaction is always, sometimes, or never spontaneous.  Explain your reasoning to support your answer.   CaCl2(s) 🡪 Ca2+(aq) + 2 Cl-(aq) + 82.9 kJ/mol

• Never

• At Hi Temp

• at Low Temp

• Always