What mass of potassium hydroxide is needed to react with 980 g of 20% phosphoric acid solution?

| April 27, 2021 | education

Let’s find the mass of the substance (H3PO4) in solution by the formula:

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

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

m (substance) = (980 g × 20%): 100% = 196 g.

Find the amount of phosphoric acid substance.

n = m: M.

M (H3PO4) = 3 + 31 + 64 = 98 g / mol.

n = 196 g: 98 g / mol = 2 mol.

Let’s compose the equation of the reaction between phosphoric acid and potassium hydroxide.

H3PO4 + 3KON = K3PO4 + 3H2O.

For 1 mol of phosphoric acid, there are 3 mol of potassium phosphate.

The substances are in quantitative ratios of 1: 3. The amount of KOH substance will be 3 times more than the amount of phosphoric acid substance.

n (KOH) = 3 n (H3PO4) = 2 × 3 = 6 mol.

We find the mass of KOH by the formula: m = n × M,

M (KOH) = 56 g / mol.

m = 56 g / mol × 6 mol = 336 g.

Answer: 336 g.



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