Will Caso4 precipitate if 50 ml of 0.0010 mol/L cacl2 (aq) is added to 50 ml of 0.010 mol/L Na2 So4 (aq)?

Question

Will Caso4 precipitate if 50 ml of 0.0010 mol/L cacl2 (aq) is added to 50 ml of 0.010 mol/L Na2 So4 (aq)?

ksp for Caso4 =2.4*10^-5

a)no precipitation will occur

b)There is not enough information given

c)precipitation will occur

d)it is at equilibrium

Answer 1

To determine whether precipitation will occur or not, you have to calculate Q, the reaction quotient. This is bases on the amount of each ion (Ca²⁺ and SO₄^2-) are present and compare this value with the K_sp. If Q > K then pptn will occur; if Q < K pptn will not occur; if Q = K then it's at equilibrium (and a ppt will form as well. As a matter of fact, if there is a ppt, then the system is at equilibrium.)

So: [Ca²⁺] = (1 x 10^-3n/1 L) (5 x 10^-2L)/(1 x 10^-1L of solution) = 5 x 10^-4 M

[SO₄^2-] = (1 x 10^-2n/1 L) (5 x 10^-2L)/(1 x 10^-1L of solution) = 5 x 10^-3 M

Q = [Ca²⁺][SO₄^2-] = (5 x 10^-4) (5 x 10^-3) = 2.5 x 10^-6

K_sp = 2.4 x 10^-5 Since Q < K then NO ppt.(choice a)