Question

Hydrochloric acid is treated with a metal to produce hydrogen gas. Suppose a student carries out this reaction and collects a volume of 154.4 × 10⁻³ dm³ of a gas at a pressure of 742 mm of Hg at a temperature of 298 K. What mass of hydrogen gas (in mg) did the student collect?

Answer 1

Given, V = 154.4 × 10⁻³ dm³

P = 742 mm of Hg

T = 298 K

m = ?

n = `"PV"/"RT"`

= `(742  "mm Hg" xx 154.4 xx 10^-13  "L")/(62  "mm Hg L K"^-1 "mol"^-1 xx 298  "K")`

= 0.006 mol

n = `"Mass"/("Molar mass")`

Mass = n × Molar Mass

= 0.0006 × 2.016

= 0.0121 g

= 12.1 mg