Question

What quantity (in mL) of a 45% acid solution of a monoprotic strong acid must be mixed with a 20% solution of the same acid to produce 800 mL of a 29.875% acid solution?

Options

• 320

• 325

• 316

• 330

Answer 1

316

Explanation:

Let N mL 45% acid is used,

mL for 20% acid = 800 − N

Hence, using the concentration formula,

45N + 20(800 − N) = 800 × 29.875

∴ 45N + 16000 − 20N = 23900

25N = 23900 − 16000

N = `7900/25` = 316 mL

Hence 316 mL of 45% concentration acid should be mixed with 20% of the solution of the same acid to produce 800 mL of a 29.875% acid solution.