A and B are ideal gases . The molecular weights of A and B are in the ratio of 1:4.The pressure of a gas mixture containing equal weights of A and B is p atm . What is the partial pressure (in atm ) of B in the mixture.

(a)p/5

(b)p/2

(c)p/2.5

(d)3p/4

Asked by Balbir | 21st Jul, 2019, 01:39: PM

Expert Answer:

Given:
 
Molecular weights of gases A and B are in the ratio of 1:4.
 
Let,
 
Molecular weight of gas A = 'x'
 
Molecular weight of gas B = '4x'
 
The mixture gases conatins equal weights of gas A and gas B
 
Let,
 
Weight of gas A = Weight of gas B = 'm' gm
 
Let total pressure be 'P'
We know
 
To calculate the partial pressure of gas B in the mixture, lets first calculate the mole fraction of gas B.
 
Mole fraction of gas B 
 
equals space fraction numerator begin display style bevelled fraction numerator straight m over denominator 4 straight x end fraction end style over denominator begin display style bevelled fraction numerator straight m over denominator 4 straight x end fraction plus bevelled straight m over straight x end style end fraction

equals space 1 fifth

straight P subscript straight B space equals space Mole space fraction space of space straight B space cross times space Total space pressure

space space space space space equals straight P over 5

Answered by Varsha | 21st Jul, 2019, 11:22: PM

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