Calculate the number of moles of CuBr which will dissolve in 0.010M HBr?

Question

Calculate the number of moles of CuBr which will dissolve in 0.010M HBr. Ksp for CuBr is 5.3x10-9.

Where do I begin!? Please help. I'm very confused.

Answer 1

The equilibrium is :
CuBr <-----> Cu+ + Br-
and the requirement for this equilibrium is that
Ksp = [Cu+] [ Br-]
HBr >> H+ + Br-. This gives us 0.010 M of Br-.
Let x = moles/L of CuBr that dissolve. We have x moles/L of Cu+ and x+ 0.010 moles/L of Br-
Substituting these values in the Ksp expression :
5.3 x 10^-9 = (x) ( x + 0.010 )
x = 5.3 x 10^-7 M
This is the molar solubility . In 1 L can dissolve 5.3 x 10^-7 moles

Answer 2

The number of moles of CuBr which will dissolve in one litre of 0.01M HBr (which isn't stated in the question) is 5.3 x 10-9/0.010.