Question

a hydrocarbon contains 80% carbon.If the molar mass of the hydro carbon is 30U derive empirical formula and molecular formula

Answer 1

Explanation:

hydorocarbon has hydrogen and carbon

if carbon % is 80 then hydrogen % is 100 -80 is 20

which means 100g of th compound will contain 80g of C and 20g of H

At.mass of C is 12 and H is 1

no. of moles of C is 80/12 = 6.67

no. of moles of H is 20/1 = 20

to obtain a simple ratio both numbers are divided by the smallest of two, which is 6,67 here

C:H = 1:2.9

2.9 is rounded to 3 since we need a ratio

C:H = 1 : 3

so empirical formula i.e simplest formula is CH3

Empirical mass 12 + 3*1=15

Molecular formula= nEmpiricalformula

n = Molar mass (given qn)/ Empirical mass

n= 30/15 = 2

Molecular formula is 2CH3

i.e C2H6

Ethane

Answer 2

Empirical formula i.e simplest formula is CH3

Molecular formula is $C2H6$

Explanation:

Hydorocarbon are those which has hydrogen and carbon

if carbon % is 80 then hydrogen % is 100 -80 is 20

which means 100g of th compound will contain 80g of C and 20g of H

At.mass of C is 12 and H is 1

no. of moles of C is 80/12 = 6.67

no. of moles of H is 20/1 = 20

to obtain a simple ratio both numbers are divided by the smallest of two, which is 6,67 here

C:H = 1:2.9

2.9 is rounded to 3 since we need a ratio

C:H = 1 : 3

so empirical formula i.e simplest formula is CH3

Empirical mass 12 + 3*1=15

Molecular formula= nEmpiricalformula

n = Molar mass (given qn)/ Empirical mass

n= 30/15 = 2

Molecular formula is 2CH3

i.e C2H6  Ethane

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