ch14 - PROBLEM 14.1 KNOWN Mixture of O2 and N2 with partial...

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PROBLEM 14.1 KNOWN: Mixture of O 2 and N 2 with partial pressures in the ratio 0.21 to 0.79. FIND: Mass fraction of each species in the mixture. SCHEMATIC: 2 O N2 p 0.21 p 0.79 = 2 O 32 kg/kmol = M 2 N 28 kg/kmol = M ASSUMPTIONS: (1) Perfect gas behavior. ANALYSIS: From the definition of the mass fraction, i i i i m r r r r = = Σ Hence, with ( 29 i i i i i i i p p p . R T / T T r = = = M M Hence i i i i i p / T m p / T = Σ M M or, cancelling terms and dividing numerator and denominator by the total pressure p, i i i i i x m . x = Σ M M With the mole fractions as 2 2 O O 0.21 x p / p 0.21 0.21 0.79 = = = + 2 2 N N x p / p 0.79, = = find the mass fractions as 2 O 32 0.21 m 0.233 32 0.21 28 0.79 × = = × + × < 2 2 N O m 1 m 0.767. = - = <
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