# Exam 4 - Livasy, David – Exam 4 – Due: Nov 15 2006,...

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Unformatted text preview: Livasy, David – Exam 4 – Due: Nov 15 2006, 4:00 pm – Inst: Donna C Lyon 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points For the reaction H 2 (g) + Cl 2 (g) → 2 HCl(g) at constant temperature and pressure, we would expect 1. Δ H < Δ E . 2. Δ H ≥ Δ E . 3. Δ H = Δ E . correct 4. Δ H > Δ E . 5. Δ H ≤ Δ E . Explanation: The equation that relates Δ H to Δ E is Δ E = Δ H- (Δ n ) R T . As 2 moles of gaseous reactants (1 mol of H 2 and 1 mol of Cl 2 ) become 2 moles of gaseous product, Δ n must be 0. This means that the term (Δ n ) R T will become zero, and Δ H and Δ E will become equal. 002 (part 1 of 1) 10 points Combustion reactions can be exothermic or endothermic. 1. False correct 2. True Explanation: 003 (part 1 of 1) 10 points Consider the following substances: HCl(g) F 2 (g) HCl(aq) Na(s) Which response includes ALL of the sub- stances listed that have Δ H f = 0? 1. HCl(g), Na(s), HCl(aq) and F 2 (g) 2. Na(s) and F 2 (g) correct 3. HCl(g) and Na(s) 4. Na(s) 5. HCl(g), Na(s) and F 2 (g) Explanation: Δ H f = 0 for elements in their standard states. This would be true for both Na(s) and F 2 (g). 004 (part 1 of 1) 10 points Heat flow is considered positive when heat flows (into, out of) a system; work is consid- ered positive when work is done (by, on) a system. 1. into; on correct 2. into; by 3. out of; by 4. out of; on Explanation: Heat flow q is considered positive when heat flows into a system. Work w is considered positive when work is done on a system. 005 (part 1 of 1) 10 points If 8000 calories of heat are added to 200 g of water at 20 ◦ C, what is the final temperature of the water? 1. 20 ◦ C 2. 80 ◦ C 3. 60 ◦ C correct 4. 40 ◦ C Explanation: Livasy, David – Exam 4 – Due: Nov 15 2006, 4:00 pm – Inst: Donna C Lyon 2 q = 8000 cal m = 200 g T ini = 20 ◦ C SH water = 1 cal/g · ◦ C 8000 cal 200 g · g · ◦ C 1 cal = 40 ◦ C is the change in temperature, not the final temperature. Heat is added to the system, so T final = 20 ◦ C + 40 ◦ C = 60 ◦ C 006 (part 1 of 1) 10 points The standard molar heat of fusion of ice is 6020 J/mol. Calculate q , w , and Δ E for melting 1.00 mol of ice at 0 ◦ C and 1.00 atm pressure....
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## This note was uploaded on 10/31/2009 for the course CH 56435 taught by Professor Flowers during the Spring '08 term at University of Texas.

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Exam 4 - Livasy, David – Exam 4 – Due: Nov 15 2006,...

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