Final_rev2-solutions

# Final_rev2-solutions - Version 298 – Final rev2 – laude...

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Unformatted text preview: Version 298 – Final rev2 – laude – (51635) 1 This print-out should have 60 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 5.0 points The phase diagram for CO 2 is given below. Solid Liquid Vapor Temperature, K Pressure,atm The triple point is at 5.1 atm and 217 K. What happens if CO 2 ( ℓ ) at 25 atm and 350 K is released into a room at 1 atm and 298 K? 1. The liquid freezes. 2. The liquid remains stable. 3. The liquid and vapor are in equilibrium. 4. The liquid and solid are in equilibrium. 5. The liquid vaporizes. correct Explanation: 002 5.0 points Which of the following statements is/are always true concerning K w ? I) It gets larger as the temperature in- creases II) It equals 10 − 14 III) K w = [H + ][OH − ] 1. II only 2. I, II 3. III only 4. I, II, III 5. II, III 6. I, III correct 7. I only Explanation: All equilibrium processes are temperature dependent, and because auto-protolysis is en- dothermic, K w increases as temperature in- crease. Thus statement I is true, but state- ment II is only true at room temperature. Statement III is the definition of K w . 003 5.0 points Consider the equations Ag + (aq) + e − → Ag(s) E ◦ = 0 . 80 V Fe 3+ (aq) + e − → Fe 2+ (aq) E ◦ = 0 . 77 V Cu 2+ (aq) + 2 e − → Cu(s) E ◦ = 0 . 34 V Which is the strongest reducing agent? 1. Ag + 2. Cu correct 3. Cu 2+ 4. Ag 5. Fe 2+ Explanation: The strongest reducing agent must produce e − the best. That is an oxidation reaction and Cu 2+ (aq) + 2 e − → Cu(s) has the most positive value (- . 34 V vs- . 77 V and- . 80 V). The ions listed (Ag + , Cu 2+ , Fe 2+ ) can- not reduce something else because they would have to donate e − and go to even higher oxi- dation states. Only the metals are candidates. 004 5.0 points Consider the irreversible reaction Version 298 – Final rev2 – laude – (51635) 2 A + 2 B → 3 C . Which of the following correctly expresses the rate of change of [B] ? 1. Δ[B] Δ t = +2 (rate of rxn) 2. Δ[B] Δ t =- 2 (rate of rxn) correct 3. Δ[B] Δ t = +(rate of rxn) 4. Δ[B] Δ t =- (rate of rxn) 5. Δ[B] Δ t =- 1 2 (rate of rxn) 6. Δ[B] Δ t = + 1 2 (rate of rxn) Explanation: As B is a reactant and consequently disap- pears during the reaction, its rate of change will be negative and the inverse of the coeffi- cient is used when writing the rate: (rate of rxn) =- 1 2 Δ[B] Δ t- 2 (rate of rxn) = Δ[B] Δ t 005 5.0 points 0.5 M of HCOOH is dissolved in water. Which equation describes a possible mass balance equation for this system? 1. C HCOOH = [HCOOH] + [HCOO − ] cor- rect 2. C HCOOH = [HCOO − ] + [H + ] 3. C HCOOH = [HCOOH] 4. C HCOOH = [HCOOH] + [HCOO − ] + [H + ] 5. C HCOOH = [HCOO − ] Explanation: 006 5.0 points Blood, sweat, and tears are about 0.15 M in sodium chloride. Estimate the osmotic pressure of these solutions at 37 ◦ C. The gas constant is 0.0821 L · atm · mol − 1 · K − 1 ....
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Final_rev2-solutions - Version 298 – Final rev2 – laude...

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