Calculate mass of hydrochloric acid (HCl) needed to prepare 100 ml solution with pH equal to 1.5

General information:
HCl is a strong acid. It completely ionizes (dissociates) in solution to produce hydronium and chloride ions. It has a molar mass (molecular weight) equal to 36.46 g/ mole.

Calculations:
Molar concentration for HCl solution with pH equal to 1.5 is calculated as the following:

pH = -log[H₃O⁺]
[H₃O⁺] = 10^-pH

[HCl] = [H₃O⁺] = 10^-1.5 = 0.032 mole/ liter

Number of moles and mass of HCl needed to make 100 ml solution with a concentration of 0.032 mole/ liter are calculated as the following:

Volume of solution in liters = 100 ml × (0.001 liter/ ml) = 0.1 liter
Number of moles = concentration × volume = (0.032 mole/ liter) × 0.1 liter = 0.0032 mole

Mass of HCl = number of moles × molar mass = 0.0032 × (36.46 g/ mole) = 0.12 g

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