Question

A certain organic substance used as a solvent in many reactions contains carbon, hydrogen, oxygen and sulphur. Weight % of hydrogen the compound is 7.7. The weight ratio C:0:S = 3:2:4. What is the least possible molar mass of the compound?

JEE/Engineering Exams

Chemistry

Solution

161

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Asemme theee is in g of soluent [ begin{array}{l} text { Mass of hydogen = } 100 times 0.077=7.7 mathrm{g} text { No. of moles of } 1=7.7 mathrm{mgl} text { iman of calben }=(100-7.7)=x frac{3}{3+2+4} end{array} ] No. of moles of ( c=frac{30.8}{12.0}=2.57 ) mol Mole ratio of ( n: c=2 ). 7: 2.57 ( =3: 1 ) Mole ratio of ( c: 0: 5=frac{3}{12.0}: frac{2}{16.0}: frac{4}{32.1} ) [ begin{array}{l} =0.25: 0.125: 0.125 =2: 1: 1 end{array} ] Thus, mole ratio of ( H: C: 0: 5=6: 2: 1: 1 ) The mol. formita of soluent is thes ( left(c_{2} H_{6} text { os }right)_{n} ), whese ( n ) is fue integer Molar mas = Maro of solvent ( =frac{100}{frac{2.57}{2 n}} ) ( =77.8 ) ngmol ( = ) Least molar mass