Question

What is the nickel ion concentration in a solution prepared by mixing 343 mL of 0.443 M nickel nitrate with 445 mL of 0.296 M sodium hydroxide? The Ksp of nickel hydroxide is 1 × 10-16

Answer 1

The equation describing the reaction is: Ni(NO₃)₂ + 2 NaOH → Pb(OH)+ 2 NaNO₃ - note that we need twice as many moles of NaOH as moles of Ni(NO₃).

Let's see how many moles of the reagent we have. moles = M x V
Pb(NO₃)₂: 0.443-mol/L x 0.343-L = 0.152 mol Ni(NO₃)₂
NaOH: 0.296-mol/L x 0.445-L = 0.132 mol NaOH

Since the amount of NaOH is not twice the amount of Pb(NO₃)₂,we will use all of the NaOH(0.132-mol) and half of that 0.066-mol of Ni(NO₃)₂. That will leave 0.152-mol - 0.066 mol = 0.086-mol Ni(NO₃)₂ still in solution.

The 0.086-mol Ni(NO₃)₂ is dissolved in 343-mL + 445-mL = 788-mL of solution. The concentration is 0.086-mol / 0.788-L = 0.109 M Ni(NO₃)₂