# When an excess of potassium hydroxide solution was added to the solution of copper nitrate ll with a mass fraction of 4%

When an excess of potassium hydroxide solution was added to the solution of copper nitrate ll with a mass fraction of 4%, a precipitate weighing 4.9 g was formed. Determine the mass of the original salt solution.

1. When potassium hydroxide is added to copper nitrate, the reaction proceeds:

Cu (NO3) 2 + 2KOH = Cu (OH) 2 ↓ + 2KNO3;

2. Let’s calculate the chemical amount of sediment:

n (Cu (OH) 2) = m (Cu (OH) 2): M (Cu (OH) 2);

M (Cu (OH) 2) = 64 + 2 * 17 = 98 g / mol;

n (Cu (OH) 2) = 4.9: 98 = 0.05 mol;

3. Determine the amount of copper nitrate:

n (Cu (NO3) 2) = n (Cu (OH) 2) = 0.05 mol;

4. Let’s calculate the mass of copper nitrate:

m (Cu (NO3) 2) = n (Cu (NO3) 2) * M (Cu (NO3) 2);

M (Cu (NO3) 2) = 64 + 2 * 14 + 6 * 16 = 188 g / mol;

m (Cu (NO3) 2) = 0.05 * 188 = 9.4 g;

5. Find the mass of the original salt solution:

m (solution Cu (NO3) 2) = m (Cu (NO3) 2): w (Cu (NO3) 2) = 9.4: 0.04 = 235 g.