Question

. A compound contains 20% hydrogen,& 80% carbon and. Its molecular mass is 30g. The molecular formula of the compound is ​

Answer 1

Answer:

the molecular formula of the compound is C2H6

Answer 2

Answer:

Let the mass of unknown compound be 100 g.

Given that the compound contains 80% of carbon and 20% of hydrogen.

Therefore, weight of carbon in the compound =80g

weight of hydrogen in the compound =20g

Molecular weight of carbon =12g

Molecular weight of hydrogen =1g

∴ moles of carbon in the compound =  12/ 80 =6.67

Moles of hydrogen in the compound =  20 /1 =20

Ratio of no. of moles of carbon to no. of moles of hydrogen-

No. of moles of carbon : no. of moles of hydrogen =6.67:20≈1:3

∴ 3 moles of hydrogen are present in the compound for 1 mole of carbon.

Hence, the empirical formula of the compound is CH  3

empirical mass=15 g/mol

Molecular formula =(CH  3 ) n

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whereas, n=  empirical mass /molecular mass =  15 /30 =2

Thus, the molecular formula of the compoud is C 2  H  6

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