# A portion of nickel weighing 8.85 g was calcined in a stream of oxygen to obtain nickel (II) oxide, then treated

A portion of nickel weighing 8.85 g was calcined in a stream of oxygen to obtain nickel (II) oxide, then treated with an excess of hydrochloric acid. Sodium sulfide solution was added to the resulting solution until precipitation ceased. Determine the mass of this sediment.

Given:
m (Ni) = 8.85 g

To find:
m (draft) -?

Solution:
1) 2Ni + O2 => 2NiO;
NiO + 2HCl => NiCl2 + H2O;
NiCl2 + Na2S => NiS ↓ + 2NaCl;
2) n (Ni) = m (Ni) / M (Ni) = 8.85 / 59 = 0.15 mol;
3) n (NiO) = n (Ni) = 0.15 mol;
4) n (NiCl2) = n (NiO) = 0.15 mol;
5) n (NiS) = n (NiCl2) = 0.15 mol;
6) m (NiS) = n (NiS) * M (NiS) = 0.15 * 91 = 13.65 g.

Answer: The mass of NiS is 13.65 g.

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