Answer to Question #198785 in Chemistry for Jerry

Question

Krypton-87 has rate constant of 1.5 x 10 -4 / s. What is the activity of a 2.0 mg sample?

Answer 1

Solution:

Krypton-87 (86.91 g/mol)

Convert the 2.00 mg sample of krypton-87 into numbers of atoms:

(2.00 mg Kr-87)(1g / 1000 mg)(1 mol Kr-87 / 86.91 g)(6.022×10²³ atoms/mol) = 1.3858×10¹⁹ atoms

Use the rate equation to calculate the activity:

r = (1.5×10^-4 s^-1)(1.3858×10¹⁹ atoms) = 2.0787×10¹⁵ atoms decay s^-1

Convert atoms s^-1 into curies (Ci):

(2.0787×10¹⁵ atoms s^-1)(1 Ci / 3.700×10¹⁰ atoms s^-1) = 56181.1 Ci

Answer: 56181.1 curies