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Use the References to access important values if needed for this question The fo

ID: 1027638 • Letter: U

Question

Use the References to access important values if needed for this question The following initial rate data are for the reaction of tertiary butyl bromide with hydroxide ion at 55 °C: (CH3)3CBr+OH(CH COH +Br Experiment 0.366 0.366 0.732 732 0.256 512 0.256 0.512 Initial Rate, Ms 4.06× 10-3 4.06x103 8.13x103 13x10-3 Complete the rate law for this reaction in the box below Use the form kIAIIBI, where 'I' is understood for m or n and concentrations taken to the zero power do not appear. Don't enter 1 for m or n Rate From these data, the rate constant is Submit Answer Retry Entire Group 5 more group attempts remaining

Explanation / Answer

For the given reaction,

(CH3)3CBr + OH- ---> (CH3)3COH + Br-

studying the data in the table,

From Experiment 1 and 3, [OH-] = constant, [(CH3)3CBr] is doubled, the rate also doubled, so the order with respect to [(CH3)3CBr] = 1

From Experiment 1 and 2, [OH-] = doubled, [(CH3)3CBr] = constant, the rate remained the same, so the order with respect to [OH-] = 0

The rate eqation thus would be,

rate = k[(CH3)3CBr]

Rate constant k = rate/[(CH3)3CBr]

                          = 4.06 x 10^-3 M.s-1/0.366 M

                          = 0.0111 s-1

----

For the oxidation of arsenate ion by Ce(IV),

studying the data in the table,

From Experiment 1 and 2, [Ce^4+] = constant, [AsO3^3-] is doubled, the rate also doubled, so the order with respect to [AsO3^3-] = 1

From Experiment 1 and 3, [Ce^4+] = doubled, [AsO3^3-] = constant, the rate increased four times, so the order with respect to [Ce^4+] = 2

The rate eqation thus would be,

rate = k[Ce^4+][AsO3^3-]^2

Rate constant k = rate/[Ce^4+][AsO3^3-]^2

                          = 2.93 x 10^-3 M.s-1/(1.62 x 10^-2 M)(0.569 M)^2

                          = 0.559 M^-2.s^-1