Find the amount of NaOH.
M (NaOH) = 40 g / mol.
n = m: M.
n = 8.7 g: 40 g / mol = 0.217 mol.
Let’s compose the reaction equation. Let’s find the quantitative ratios of substances.
NaOH + HCl = NaCl + H2O.
According to the reaction equation, 1 mol of NaOH accounts for 1 mol of HCl. Substances are in quantitative ratios 1: 1.
n (NaOH) = n (HCl) = 0.217 mol.
Let’s find the mass of НCl.
m = n × M,
M (HCl) = 36.5 g / mol.
m = 0.217 mol × 36.5 g / mol = 7.92 g.
Answer: 7.92 g.
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