Posted by **Confused** on Saturday, November 20, 2010 at 10:36pm.

The rate of the following reaction:

Radioactive decay of 90Sr,

is characterized by the rate constant k = 0.024 year-1. What is the half-life (in years) for this reaction at the same conditions when the initial concentrations are 0.0356 M? (Round your answer to 3 significant figures.)

Hint: The units of the rate constant are linked with the order of reaction.

Answer:________________years

- Concentration and Reaction -
**DrBob222**, Saturday, November 20, 2010 at 11:10pm
Radioactive decay is a first order reaction. t_{1/2} = 0.693/k

Solve for t_{1/2}.

It doesn't matter that conditions are changed, the half-life is the same; half life of first order reactions don't depend upon the initial concn. You can show that, however, by using

ln(No/N) = kt

Substitute 0.0356 M for No and half that for N and 0.024 for k. t_{1/2} will be the same as obtained by 0.693/0.024.

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