Question

A class is given a demonstration of solution chemistry and solubility equilibria.Passage: A 6.57-g sample of NiSO4•6H2O (molar mass 262.84) is dissolved in enough water to make 50.00 mL of a green solution, and 7.15 g of Na2CO3•10H2O (molar mass 286.14) is dissolved in enough water to make 50.00 mL of a colorless solution. The two solutions are mixed, and a green precipitate forms. The resulting slurry is divided into two equal portions. To one portion is added an excess of 6 M HCl, which results in the disappearance of the precipitate and a rapid evolution of a gas. To the second portion is added a few milliliters of 6 M NH3. The precipitate dissolves, and a blue solution forms.Question: According to the information in the passage, the gas that evolves is:A) sulfur dioxide. B) sulfur trioxide. c) carbon dioxide. D) carbon monoxide.

Answer 1

Answer:

The gas that evolves must be carbon dioxide.

Explanation:

There is two reactions taking place: first, nickel sulfate reacts with sodium carbonate yielding sodium sulfate and nickel carbonate, which is a green solid. Then nickel carbonate reacts with hydrochloride, yielding nickel chloride, carbon dioxide and water.

1) NiSO4 (aq) + Na2SO4 (aq) = NiCO3 (s) + Na2SO4

2) NiCO3 (s) + 2 HCl (aq) = NiCl2 + CO2 + H2O