Question

Complete combustion of 1.80 g of an oxygen containing compound (C$_x$H$_y$O$_z$) gave 2.64 g of CO$_2$ and 1.08 g of H$_2$O. The percentage of oxygen in the organic compound is :

• A. 50.33
• B. 53.33
• C. 63.53
• D. 51.63

Hint:

In combustion analysis, always find the masses of C and H first. If the sum is less than the total sample mass, the remainder is Oxygen (assuming no other elements are present).

Answer 1

The Correct Option is B

Step 1: Find mass of Carbon: $W_C = \frac{12}{44} \times 2.64 = 0.72$ g.
Step 2: Find mass of Hydrogen: $W_H = \frac{2}{18} \times 1.08 = 0.12$ g.
Step 3: Find mass of Oxygen by subtraction: $W_O = 1.80 - (0.72 + 0.12) = 1.80 - 0.84 = 0.96$ g.
Step 4: Calculate percentage: $%O = \frac{0.96}{1.80} \times 100 = 53.33%$.