Chemistry HW 11 - ekk86 hw11 Holcombe (53570) This...

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ekk86 – hw11 – Holcombe – (53570) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. R =8 . 314 J mol - 1 K - 1 1 cal = 4.184 J 001 10.0 points The rate oF the reaction 2O 3 3O 2 is equal to 1. + 1 2 Δ[O 3 ] Δ t . 2. - Δ[O 2 ] Δ t . 3. - 1 2 Δ[O 3 ] Δ t . correct 4. - Δ[O 3 ] Δ t . 5. - 1 3 Δ[O 2 ] Δ t . Explanation: The rate oF a chemical reaction can either be expressed as the rate oF disappearance oF a reactant (as in this case) or as the rate oF appearance oF a product. However, this rate is multiplied by the inverse oF the coeF- fcient oF the species in question. The nega- tive sign here reminds us that as the reaction progresses, this species is consumed and de- creases in concentration. 002 10.0 points When the reaction 3 NO(g) N 2 O(g) + NO 2 (g) is proceeding under conditions such that 0.015 mol/L oF N 2 O is being Formed each second, the rate oF the overall reaction is ? and the rate oF change For NO is ? . 1. 0.015 M · s - 1 ; - 0.005 M · s - 1 2. none oF the other answers is correct 3. 0.015 M · s - 1 ; - 0.045 M · s - 1 correct 4. 0.015 M · s - 1 ; +0.045 M · s - 1 5. 0.030 M · s - 1 ; - 0.005 M · s - 1 Explanation: Notice that three moles oF NO are required to make one mole oF N 2 O in this reaction, so the rate oF disappearance oF NO (which has a negative sign) is three times the rate oF appearance oF N 2 O. 003 10.0 points Which oF the Following does not a±ect the rate oF a reaction? 1. the value oF E a 2. the value oF Δ H rxn correct 3. the presence oF a catalyst 4. the temperature oF the reactants Explanation: Δ H is a state Function; it is independent oF the path. 004 10.0 points Consider the irreversible reaction A + 2 B 3C . 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 = - 1 2 (rate oF rxn) 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 = - 2 (rate oF rxn) correct
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ekk86 – hw11 – Holcombe – (53570) 2 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 coeF- 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 10.0 points Suppose a compound is involved in three di±erent reactions denoted R 1 , R 2 , and R 3 . Tripling the concentration of this reactant in all three reactions causes the rates of reaction to increase by factors of 3, 9, and 1, respec- tively. What is the order of each reaction with respect to this reactant? 1. R 1 = 1; R 2 = 2; R 3 =0 correct 2. R 1 = 0; R 2 = 1; R 3 =2 3. R 1 = 3; R 2 = 9; R 3 =1 4. R 1 = 2; R 2 = 0; R 3 5. R 1 = 1; R 2 = 3; R 3 Explanation: Tripling the concentration of the reactant in R 1 brings about a tripling (= 3 1 ) increase in the rate of the reaction, so the reaction is frst order with respect to the reactant in this case.
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Chemistry HW 11 - ekk86 hw11 Holcombe (53570) This...

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