A researcher needs 5.00 mg of ¹²⁸Ba for an experiment.If the half-life of ¹²⁸Ba is 2.43 days,how many milligrams of ¹²⁸BaCl₂ must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of ¹²⁸Ba is 128 g/mol. )

Question

Quizplus · Accepted Answer

We can use the following equation to calculate the amount of ¹²⁸BaCl₂ that needs to be ordered: Amount needed = Amount initial x (1/2)^(t/t1/2) Where t is the total time required (4.50 days for shipping + 2.43 days half life = 6.93 days), t1/2 is the half-life (2.43 days) and the initial amount is 5.00 mg. Plugging in these values, we get: Amount needed = 5.00 mg x (1/2)^(6.93/2.43) = 18.0 mg Therefore, the researcher should order 18.0 mg of ¹²⁸BaCl₂ from the manufacturer. The answer is option B.

A Researcher Needs 5