To a solution with a mass fraction of sodium hydroxide of 5%, an excess of copper sulfate solution 2 was added

To a solution with a mass fraction of sodium hydroxide of 5%, an excess of copper sulfate solution 2 was added, while a precipitate weighing 4.9 was formed, determine the mass of the initial alkali solution

The equation for this reaction is:
2 * Na OH + Cu S O4 = Na2 SO4 + Cu (OH) 2 (this will be a precipitate)
find the chemical properties of this residue
mass (Cu (OH) 2) = 4. 9 grams / 160 grams / mol = 4.9 / 160 mol = 0. 05 mol
then the proportion is:
x / 2 = 0. 05/1;
multiply the values cross by cross, then
x * 1 = 2 * 0, 0 5
x = 2 * 0, 0 5
x = 0. 1 mole
then
mass (Na OH) = 0. 1 mol * (23 + 17) grams / mol = 0.1 * (23 + 17) grams = 0.1 * 40 grams = 4 grams;
the mass of the alkali solution is: 4 grams / 0. 0 5 = 400/5 grams = 80 grams.
Answer: Mass (NaOH) = 80 grams.