Question

6.00 g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 26. g/mol, is burned completely in excess oxygen, and the mass of the products carefully measured:

product mass
carbon dioxide 20.31g
water 4.16 g
Use this information to find the molecular formula of X

Answer 1

C2H2

Step-by-step explanation:

Mass of Carbon in CO2
`= (12/44) (20.31)` grams
`= 5.54` gram

Mass of hydrogen in H2O
`= (2/18)(4.26)` grams
`= 0.46` gram

We will calculate the % of C and H in the sample

% C
`= (5.54/6) * 100 = 92`%

% H
`= (0.46/6)*100 = 7.7`%

Number of mole of C
`= 92/12 = 7.69`

Number of mole of H
`= 7.67/1 = 7.67`

Fractional share of C
`= 7.69/7.67 = 1`

Fractional share of H
`= 7.67/7.67 = 1`

Empirical Formula = CH

Empirical Mass
`= 12+1 = 13`

Molecular mass
`= 26`

Molecular Formula – CHn

N
`= 26/13 = 2`

Molecular Formula = C2H2