Helium-oxygen mixtures are used by divers to avoid the bends and are used in medicine to...

Helium-oxygen mixtures are used by divers to avoid the bends and are used in medicine to treat some respiratory ailments. What percent (by moles) of He is present in a helium-oxygen mixture having a density of 0.508 g/L at 25 ∘C and 721 mmHg?

Express your answer numerically as a percentage.

Solutions

Expert Solution

PV = nRT

P = 721/760 = 0.9486atm

R = 0.0821L-atm/mole-K

T = 25+273 = 298K

V =1L

PV = nRT

n = PV/RT

= 0.9486*1/0.0821*298 = 0.0387moles

find no of moles of helium using molar masses

0.508 = X*4g/mole of He + (0.0387-X)*32g/mole of O2

X         = 0.026

X    = 0.026 moles of He

He%    = no of moles of He*100/total no of moles

= 0.0262*100/0.0387 = 67.7%

queen_honey_blossom answered 1 year ago

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