An excess of copper (II) sulfate solution was added to a solution with a mass fraction of sodium hydroxide of 5%.

| March 25, 2021 | education

An excess of copper (II) sulfate solution was added to a solution with a mass fraction of sodium hydroxide of 5%. This resulted in the formation of a precipitate weighing 4.9 g. Determine the mass of the initial alkali solution.

1. When adding copper sulfate (2) to an alkali solution, the following reaction occurs:

2NaOH + CuSO4 = Cu (OH) 2 ↓ + Na2SO4;

2.determine the chemical amount of precipitated copper hydroxide:

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

M (Cu (OH) 2) = 64 + 2 * 16 + 2 = 98 g / mol;

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

3. find the amount of alkali that reacts:

n (NaOH) = n (Cu (OH) 2) * 2 = 0.05 * 2 = 0.1 mol;

4.calculate the mass of sodium hydroxide:

m (NaOH) = n (NaOH) * M (NaOH);

M (NaOH) = 23 + 16 + 1 = 40 g / mol;

m (NaOH) = 0.1 * 40 = 4 g;

5.Calculate the mass of the initial alkali solution:

mr-ra (NaOH) = m (NaOH): w (NaOH) = 4: 0.05 = 80 g.

Answer: 80 g.



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