It is statistically unlikely that any reac tion

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It is statistically unlikely that any reac- tion requiring the simultaneous collision of 3 or more molecules will occur frequently enough to contribute to the rate of the re- action. Termolecular and higher moleculari- ties would happen so infrequently that there would not be measurable rate of reaction. 020 4.0points The reaction N 2 + 3 H 2 2 NH 3 is proceeding under conditions that 0.150 moles of NH 3 are being formed every 20 sec- onds. What is the rate of disappearance of H 2 ?
1. The question cannot be answered from the information given; we need to know the volume of the container.
Explanation: n NH 3 = 0.150 mol t = 20 s The rate of appearance of NH 3 is Rate = 1 2 Δ[NH 3 ] Δ t We can consider this to be Rate = 1 2 · 0 . 150 mol 20 s = 0 . 00375 mol / s The rate of disappearance of H 2 is Rate = - 1 3 · Δ[H 2 ] Δ t 0 . 00375 mol / s = - 1 3 · Δ[H 2 ] Δ t
Version 114 – Exam 3 - S17 – labrake – (50355) 8 Δ[H 2 ] Δ t = - 0 . 01125 mol / s Thus H 2 disappears at a rate of 1 . 125 × 10 2 mol/s. 021 3.0points If Substance A is a catalyst, which equation best represents what happens in a chemical reaction? -→ Which reaction has the larger rate con- stant? 023 3.0points Consider the concentration-time dependence graph for two first-order reactions. 2 = 0 . 097 M 1 s 1 T 1 = 326 . 85 C + 273 . 15 = 600 K [A] 0 Molar Concentration of Reactant Concentration -→ Time -→ Which reaction has the larger rate con- stant? C. What is the activation energy of this reaction? k 2 = 0 . 097 M 1 s 1 T 1 = 326 . 85 C + 273 . 15 = 600 K
Version 114 – Exam 3 - S17 – labrake – (50355) 9 2 y = 64 16 = 4 = 2 2
025 4.0points The following data were collected for the re- action 2 A + B 2 + C D Initial Initial Initial Initial [A] [B 2 ] [C] rate (M) (M) (M) (M/s) 1 0 . 01 0 . 01 0 . 01 1 . 250 × 10 3 2 0 . 02 0 . 01 0 . 01 5 . 000 × 10 3 3 0 . 03 0 . 01 0 . 05 1 . 125 × 10 4 4 0 . 04 0 . 02 0 . 01 8 . 000 × 10 4 Find the rate law. 1. Rate = (1 . 25 × 10 7 ) [A] 2 [B 2 ] 2 2. Rate = (1 . 25 × 10 9 ) [A] 2 [B 2 ] 3. Rate = (1 . 25 × 10 11 ) [A] 2 [B 2 ] 2 correct 4. Rate = (1 . 25 × 10 7 ) [A] [B 2 ] [C] 2 5. Rate = (1 . 25 × 10 9 ) [A] [B 2 ] 2 y = 2 Rate 3 Rate 1 = k [A] 2 3 [B 2 ] y 3 [C] z 3 k [A] 2 1 [B 2 ]

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