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# STP chemistry problem?

What is the partial pressure of hydrogen in a flask containing 4.00 gm hydrogen and 14.0 gm nitrogen at STP? The answer should

end up as .800 atm

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convert each to moles

moles = mass / molar mass

moles N2 = 14.0 g / 28.02 g/mol = 0.500 moles

moles H2 = 4.00 g / 2.016 g/mol = 2.00 moles

the total pressure in a system = sum of partial pressure of each component gas

So the partial pressure is proportional to the amount of the gas in the sample.

The proportion of H2 = moles H2 / total moles

= 2.00 moles / 2.50 moles

= 0.8

Thus partial pressure H2 = 0.8 x total pressure

STP is standard temp (0 deg C) and pressure (1.00 atm)

partial pressure H2 = 0.8 x 1.00 atm

= 0.800 atm

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