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.

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FREE Expert Solution

Balanced equation: NaH + H2O → NaOH + H2


Dalton’s Law: 

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


Ptotal=PGas 1+PGas 2+PGas 3...Ptotal=PH2+Pwater760 mm Hg=PH2+42.2 mm Hg

PH2=717.8 mm Hg


Ideal gas equation: moles H2


PVRT=nRTRTn=PVRT

n=717.8 mm Hg ×1 atm760 mm Hg0.495 L 0.08206L·atmmol·K35°C+273.15 K

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.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Collecting Gas Over Water concept. If you need more Collecting Gas Over Water practice, you can also practice Collecting Gas Over Water practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Davis' class at VALENCIA.