Emperical Formula, Molecular Formula Examples and Answer

Emperical Formula Examples and Answer
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Emperical Formula Examples and Answer

 Emperical Formula of a compound is the simpliest possible formula giving the ratio of atoms in a molecule of the compound. Example CH, HO, NH3, H2O e.t.c.

Molecular Formula The molecular is the formula which shows the actual number of atoms of the different elements present in one molecules of the compound. Example ( CH)n, (H2CO)n, (CH3)n e.t.c

Some given solution to some test questions

1. Determine the molecular formula of an alkane whose vapour density is 15 (H=1, C=12, R.M.M = 2, VD)

A. CH4 Answer

B. C3H6

C. C2H4

D. C2H6


emperical formular of alkane = (CH4)

(1 x 12 + 4 x 1)n = 2 x 15

16n = 30

Divide both sides by 16

16n/16 = 30/16

n = 1

 2. A hydrocarbon X has a relative molar mass 56 and consists of 87.8% by mass of carbon and 12.2% hydrogen. Determine the empirical formula of X give its molecular formula


C                  H

87.8           12.2

12                1


7.32           12.2

Divide by the smallest ratio which is 12.2

1                   1   therefore Emperical formula of X is CH

Molecular formula

(12 + 1)n = 56

13n = 56

Divide both sides by 13

13n/13 = 56/13

N  = 4     therefore Molecular formular of X is C4H4

Do you know Emperical Formula Examples and Answer is among the simplest solving in chemistry?

 3. A hydrocarbon containing 88.9% carbon has the empirical formula (H=1, C=12)


B. CH2

C. C2H3

D. C2H5


C                   H

88.9             11.1

12                    1


7.4 1               11.1

Divide by the smallest ratio

1                         1        therefore the empirical formular is CH


Try this and solve

A compound contains 31.9% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formular of the compound? ( K=39, CL=35.5, O=16)

If you think what was solve here is not correct or maybe you are having a doubt about it why can’t you kindly drop it in our comment box below.

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1 Comment

  • the number 1 answers provided is wrong . the answer is C2H6

    empirical formula for alkanes is CnH2n+2

    so CnH2n+2 = molar mass
    molar mass = 2× vapour density
    molar mass= 30

    CnH2n+2 = 30
    12n + 2n + 2 = 30

    14n + 2= 30
    14n = 30 – 2
    14n = 28
    n = 28/14
    n = 2

    then plug in the value of n in the empirical formula (CnH2n+ 2)


    C2H6 is the final answer …

    to check if the answer is correct
    C2H6 = 30g/mol , which has a relative vapour density of 15

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