Thermodynamics

Thermodynamics

Question

The solubility product of silver bromide is 5.0 x 10-13. The quantity of potassium bromide (molar mass taken as 120 g mol–1)to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is

  • 1.2 x 10-10

  • 1.2 x 10-9 g

  • 6.2 x 10-5

  • 5.0 x 10-8 g

Answer

A.

1.2 x 10-10

Ksp of AgBr = [Ag+][Br-] = 5.0 x 10-13
[Ag+] = 0.05 M
left square bracket Br to the power of minus right square bracket space equals space fraction numerator 5.0 space straight x space 10 to the power of negative 13 end exponent over denominator 0.05 end fraction space equals space 1 space straight x space 10 to the power of negative 11 end exponent space straight M
Moles of KBr = 1 x 10-11 x 1 = 1 x 10-11
weight of KBr  1 x 10-11 x 120 = 1.2 x 10-19 g

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