Multiple Choice
What is the rate constant k for a first-order reaction if its half-life is 2.50 min?
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15. Chemical Kinetics
Half-Life
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If you start with 80 grams of cobalt-60, how many grams will remain after three half-lives?
A
10 grams
B
5 grams
C
40 grams
D
20 grams
Verified step by step guidance1
Identify the initial amount of the substance, which is 80 grams of cobalt-60.
Recall the concept of a half-life: after one half-life, half of the original amount of the substance remains.
Use the formula for the remaining amount after n half-lives: \(\text{Remaining amount} = \text{Initial amount} \times \left(\frac{1}{2}\right)^n\).
Substitute the given values into the formula: \(\text{Remaining amount} = 80 \times \left(\frac{1}{2}\right)^3\).
Calculate the power of one-half raised to 3, then multiply by 80 to find the remaining grams after three half-lives.
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