Question

0.2 mole of an alkane on complete combustion gave
26.4 g of CO2. The molecular weight of alkane is
(a) 16
(b) 30
(c) 44
(d) 58

Answer 1

Answer:

(c)44

Explanation:

as it is known that the law of combustion is given by

CxHy + (x+y/2)O2 ----> xCO2 + y/2H2O

so 0.2 mole of alkane ------>26.4 gm of CO2

and you Know that molecular weight of CO2 is 44gm and in this reaction we have 26.4 gm means 26.4/44=0.6 mole of CO2

actually in this reaction 0.2 mole of alkane gives 0.6 mole of CO2 so,,,

1 mole give 3 mole means value of x in xCO2 is 3 as you know the value of x i.e 3

so the formula of alkane is C3H8 as per CnH2n+2 rule

so molecular weight of alkane is 44 i.e C option is correct i.e C=12 and H=1 so 12*3+1*8=44