. For the reaction Bproducts, and an initial concentration of B of 0.10 M and a

Question

. For the reaction Bproducts, and an initial concentration of B of 0.10 M and a rate constant at 25°C of 75 ?/s, where"? means the units will depend on the order of the reaction, determine the half- life in seconds if the reaction is a) (3 pts) half-order in B b) (1 pt) first order in B Show each equation for the half-life before computing its value Now give the half-life in seconds if the initial concentration of B is 0.30 M and the reaction is c) (1 pt) half-order in B d) (1 pt) first order in B

Explanation / Answer

Given that [B] = 0.1 M

(a) k = 75 M0.5/s

Half-life (t1/2) = 21/2/k * {(2a)1/2 - a1/2}

Now, t1/2 = 21/2/75 * {(2*0.1)1/2 - 0.11/2}

= 2.47*10-3 s or 2.47 ms (millisecond)

(b) k = 75 M0/s

Half-life (t1/2) = 0.693/k

i.e. t1/2 = 0.693/75 = 9.24 ms

(c) k = 75 M0.5/s

Half-life (t1/2) = 21/2/k * {(2a)1/2 - a1/2}

Now, t1/2 = 21/2/75 * {(2*0.3)1/2 - 0.31/2}

= 4.28*10-3 s

(d) k = 75 M0/s

Half-life (t1/2) = 0.693/k

i.e. t1/2 = 0.693/75 = 9.24*10-3 s

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