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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?
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Solution
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
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