Question

Tartaric acid is the white, powdery substance that coats sour candies such as sour patch kids. combustion analysis of a 12.01-g sample of tartaric acid-which contains only carbon, hydrogen, and oxygen-produced 14.08 g co2 and 4.32 g h2o. empirical formula

Answer 1

First we calculate the mass of carbon, hydrogen and oxygen.

Mass of Carbon;
Molar mass of CO₂ is 44.009g/mol  and molar mass of C = 12.011 g/mol 

Mass of Carbon in 14.08g CO2₂ = 12.011/44.009 x 14.08 = 3.84

Mass Hydrogen;
Molar mass H₂O is 18.0015g/mol and molar mass of H is 1.008and  H₂ = 2.016 

Mass Hydrogen in 4.32g of H₂O = 2.016/18.0015 x 4.32 = 0.48

Mass of  Oxygen = total mas of tartaric acid – (mass of carbon + mass of hydrogen) = 12.01 - (3.84+0.48) = 7.69
Now divide carbon, hydrogen and oxygen through their respective atomic masses: 
C = 3.84/12.011 = 0.32
H = 0.48/1.008 = 0.48
O = 7.69/15.999 = 0.48
Now divide by smallest: 
C = 0.32/0.32 = 1 
H = 0.48/0.32 = 1.5 
O = 0.48/0.32 = 1.5 
multiply by 2 to get whole integers: 
C = 1 x 2 = 2 
H= 1.5 x 2 = 3 
O= 1.5 x 2 = 3
Thus, the Empirical formula of tartaric acid = C₂H₃O₃