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

Answer:

C2H2

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