(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The initial concentration of reactant in a first-order reaction is 0.75M. The rate constant for the reaction is 2.75/s. What is the concentration (mol/L) of reactant after 6.5s?

2. Relevant equations

-kt=[A]initial/[A]anytime

3. The attempt at a solution

-(2.75/s)(6.5s)=[0.75M]/[A]@6.5seconds

-17.875/1=0.75M/x; x= -4.20x10^-2; The answer to this problem is not right, but I do not have any idea how to go about it another way.

Problem 2.

The usefulness of radiocarbon dating is limited to 50,000 years. Show mathematically why this is true. (Hint: Remember half life follows first order kinetics. The half life of C-14 is 5.73 x 10^3 years).

Half life formula : t1/2= 0.693/k

Common integrate rate law for first order reactions: ln[A]=-kt + ln[A@ initial]

5.73x10^3 = 0.693/k, k = 1.21x10^-4/s

How would I use k in my integrated formula to prove that the half life is limited to 50,000 years?

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# Homework Help: General Chemistry questions and kinetics

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