Exercise 10 | Chemical Calculations for Solutions

Nickel(II) sulfide is insoluble in water and can be formed according to the net ionic equation:

Ni2+ (aq) + S2- (aq) → NiS (s).


Calculate the volume of 0.420 M K2S (aq) that is required to precipitate all the nickel(II) from 28.0 mL of 0.370 M NiCl2.

From the net ionic equation: 1 mole of S2- is required to precipitate 1 mole of Ni2+

⇒ nS2- = nNi2+

 

nS2- = nK2S and nNi2+ = nNiCl2

⇒ nK2S = nNiCl2

⇒ MK2S x VK2S = MNiCl2 x VNiCl2

⇒ VK2S = MNiCl2 × VNiCl2MK2S

⇒ VK2S = 0.370 × 28.00.420 = 24.7 mL