# Problem: Binary compounds of alkali metals and hydrogen react with water to liberate H2 (g). The H2 from the reaction of a sample of NaH with an excess of water fills a volume of 0.495 L above the water. The temperature of the gas is 35 oC and the total pressure is 760 mmHg .Find the mass of NaH that reacted.

###### FREE Expert Solution

Balanced equation: NaH + H2O → NaOH + H2

Dalton’s Law:

• vapor pressure of water @ 35°C = 42.2 mm Hg

${\mathbit{P}}_{{\mathbf{H}}_{\mathbf{2}}}\mathbf{=}$717.8 mm Hg

Ideal gas equation: moles H2

$\frac{\mathbf{PV}}{\mathbf{RT}}\mathbf{=}\frac{\mathbf{n}\overline{)\mathbf{RT}}}{\overline{)\mathbf{RT}}}\phantom{\rule{0ex}{0ex}}\mathbf{n}\mathbf{=}\frac{\mathbf{PV}}{\mathbf{RT}}$

n = 0.0185 mol H2

Mole to mole comparison: 1 mole NaH forms 1 mole H2

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###### Problem Details

Binary compounds of alkali metals and hydrogen react with water to liberate H2 (g). The H2 from the reaction of a sample of NaH with an excess of water fills a volume of 0.495 L above the water. The temperature of the gas is 35 oC and the total pressure is 760 mmHg .

Find the mass of NaH that reacted.