As a result of the reaction of potassium oxide with water, 120 g of a 20% alkali solution

| September 11, 2021 | education

As a result of the reaction of potassium oxide with water, 120 g of a 20% alkali solution was obtained. Determine the mass of the reacted oxide.

Let’s find the mass of alkali in the solution.

W = m (substance): m (solution) × 100%,

hence m (substance) = (m (solution) × w): 100%.

m (substance) = (120 g × 20%): 100% = 24 g.

Let’s find the amount of KOH substance.

n = m: M.

M (KOH) = 56 g / mol.

n = 24 g: 56 g / mol = 0.429 mol.

Let’s find the quantitative ratios of substances.

K2O + H2O = 2KON.

For 2 mol of KOH there is 1 mol of K2O.

Substances are in quantitative ratios of 2: 1.

The amount of K2O substance is 2 times less than that of KOH.

n (K2O) = ½ n (KOH) = 0.429: 2 = 0.21 mol.

Let’s find the mass of K2O.

m = n × M.

M (K2O) = 94 g / mol.

m = 94 g / mol × 0.21 mol = 19.74 g.

Answer: 19.74 g.



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