Question

Will a precipitate form if 55 mL of 0.0500 M AgNO3 is mixed with 60 mL of 0.0225 M NaBr? is Q greater than, equal to, or less than Ksp?

Answer 1

AgBr(s)    Ag⁺ (aq) + Br^- (aq); Ksp = 5.4 × 10⁻¹³

mol Ag⁺ (aq) = (0.055 L sol'n) (0.050 mol Ag⁺/L sol'n)

= 0.00275 mol Ag⁺

[Ag⁺] = 0.00275 mol / (55 mL + 60 mL)

= 0.00275 mol / 115 mL

= 0.00275 mol / 0.115 L

= 0.0239 M   

mol Br^-(aq) = (0.060 L sol'n) (0.0225 mol Br^-/L sol'n)

= 0.00135 mol Br^-

[Br^-] = 0.00135 mol / 0.115 L

= 0.00015525 M

Q = [Ag⁺] [Br^-]

= (0.0239) (0.00015525)

= 3.7 x 10^-6

Since, Q > Ksp;

AgBr will precipitate from solution.