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The decomposition of X has a rate constant of 0.05 microgram/year (zero order). How many years are needed for 5 microgram of X to decompose to 2.5 microgram?

Correct answer: 50

Solution

Zero-order: amount consumed (5 - 2.5 = 2.5 microgram) equals k*t, so t = 2.5/0.05 = 50 years.

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