Question

The addition of dimethylglycoxime, H2C4H6O2N2, to a solution containing nickel(II) ion gives rise to a precipitate: Ni2 2H2C4H6O2N2 Ni(H2C4H6O2N2)2 2H If 0.15 g nickel alloy is treated with dimethylglycoxime and .175 mg nickel dimethylglycoxime is collected. Determine the mass and percent of nickel in the alloy.

Answer 1

Solution :

The balanced equation is :

                              $Ni^{2+}+2H_2C_4H_6O_2N_2 \rightarrow Ni(H_2C_4H_6O_2N_2)_2+2H^+$

Molar mass           56.7            116                        290.7

From the balanced equation,

2 mole

= 2 x 116 g of $H_2C_4H_6O_2N_2$ produces 1 mole = 290.7 g of nickel dimethylglycoxime

or 2 x 116 mg of $H_2C_4H_6O_2N_2$ produces 1 mole = 290.7 g of nickel dimethylglycoxime

0.175 mg of $H_2C_4H_6O_2N_2$ produces $\frac{0.175 \times 290.7}{2 \times 116}$ = 0.219 mg of nickel dimethylglycoxime

290.7 g of $Ni(H_2C_4H_6O_2N_2)_2$ contains 58.7 mg of Ni

0.219 mg of $Ni(H_2C_4H_6O_2N_2)_2$ contains $\frac{0.219 \times 58.7}{290.7} = 0.0443$  mg of Ni

So mass of nickel, m = 0.0443 mg = $0.0443 \times 10^{-3}$ g

Percent of Nickel in the alloy = $\frac{\text{mass of nickel}}{\text{mass of alloy}} \times 100$

                                                $=\frac{0.0443 \times 10^{-3}}{0.159}\times 100$

                                               = 0.03%