You can recall that the decay of a radioactive substance is governed by the diff

Question

You can recall that the decay of a radioactive substance is governed by the differential equation dm/dt=km, where m(t) represents the mass of the substance as a function of time T, the constant k is negative. The half life of a radioactive substance is the time required for half of any given amount of the substance to decay. (No calculator needed, expression allowed)

1. What are the apropriate units for k if it is measured in days?

2. Radioactive substance strontium 90 has a half life of 28 days. find an expression for the mass m(t) of strontium-90 at arbitrary time t if the original amount is given by m(0)= Mo

3. suppose that some strontium-90 is placed into storage. 7 days after this is done, 3 grams of strontium-90 remain. How much strontium 90 was originally stored?

Explanation / Answer

1. Units of K are (days)-1

2. ln(m) = (-1/28) * ln2 * t + ln(M0)

3. M0 = 3 * 2(1/4)

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