# chemistry

A first-order reaction is 40% complete at the end of 50 minutes. What is the value of the rate constant (in min^-1)?

A. 1.8 x 10^-2
B. 1.0 x 10^-2
C. 1.2 x 10^-2
D. 8.0 x 10^-3
E. none of these

how would i approach this problem?
i know that to find the rate constant, i could use the formula k=rate/reactants, but i don't have the reactants or anything...so i don't know what to do..

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1. i would say it option (D)
if u chang 40% to .40
.40/50
=.008= 8.0x10^-3

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2. Could you do something like this?
Reactants ==> Products
100 = reactants to 0 products initially.
Then if it is 40% complete, then
100-40 = 60 reactants and 40 products. And this has occurred in 50 minutes.

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