Question

Niobium-91 has a half-life of 680 years. After 2,040 years, how much niobium-91 will remain from a 300. 0-g sample? 3 g 18. 75 g 37. 5 g 100. 0 g.

Answer 1

Answer:

Amount of Niobium-91 initially

= 300/91 =3.2967mol

2040 years = 3 ×680 = 3 half-lives

therefore, amount left = 0.4121mol

mass of Niobium-91 remaining = 0.4121 ×91 =37.5g

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