Question

6. How many grams of copper(II) phosphate will dissolve in 800. mL of water?

A) 4.4 x 10–5

B) 1.8 x 10–7

C) 1.6 x 10–8

D) 2.2 x 10–7

E) 5.0 x 10–6

Answer is E Please show work! Thank you !!

Answer 1

this question is related to solubility

Ksp of Cu3(PO4)2 = 1.4*10^-37

The salt dissolves as:

Cu3(PO4)2 <----> 3 Cu+ + 2 PO43-

   3s 2s

Ksp = [Cu+]^3[PO43-]^2

1.4*10^-37=(3s)^3*(2s)^2

1.4*10^-37= 108(s)^5

s = 1.669*10^-8 M

Molar mass of Cu3(PO4)2 = 3*MM(Cu) + 2*MM(P) + 8*MM(O)

= 3*63.55 + 2*30.97 + 8*16.0

= 380.59 g/mol

Molar mass of Cu3(PO4)2= 380.59 g/mol

s = 1.669*10^-8 mol/L

To covert it to g/L, multiply it by molar mass

s = 1.669*10^-8 mol/L * 380.59 g/mol

s = 6.353*10^-6 g/L

Here volume is 800 mL = 0.800 L

So,

mass = s*volume

= 6.353*10^-6 g/L * 0.800 L

= 5.0*10^-6 g

Answer: E