A 9.52 Times 10^-5 mol sample of rubidium-86 emits 8.87 Times 10 beta particle i

Question

A 9.52 Times 10^-5 mol sample of rubidium-86 emits 8.87 Times 10 beta particle in one hour. What is the half-life of rubidium - 86? A) 2.23 Times 10^-3 h B) 1.15 Times 10^-3 h C) 448 h D) 645 h E) none of these 27. A solution that is 0.0010 M in Fe^2e, Cd^2e, Co^2e, and Mn^2e is saturated with H_2S at a pH of 3.00. Which metals form a sulfide precipitate? (The K_p values are at follows: FeS = 6 Times 10^-11, CdS = 8 Times 10^-29, CoS = 4 Times 10^-21 and MnS = 2.5 Times 10^-19. In water, [H_2S] = 0.10 M; For H_2S, k Times K = 1.1 Times 10^-29)

Explanation / Answer

The inegration constant is related to activity as

A = X N

= integration constant = ?

A = activity = 8.87 X 1016 particles / hour

[N0] = number of particles present initially = 9.52 X 10-5 moles = 6.023 X 1023 X9.52 X 10-5 = 57.34 X 1018 particles

= A / N = 8.87 X 1016 particles /hour / 57.34 X 1018 = 1.547 X 10-3

half life = t1/2 = 0.693 / = 0.693 /1.547 X 10-3

t1/2 = 447.96 hours = 448 hours

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