Complete combustion of X g of an organic compound gave 0.25 g of CO_2 and 0.12 g of H_2 O. If the % of carbon is 25\% and of hydrogen is 4.89\%, then X = _____ 10^ -3 g. (Nearest integer) (Molar mass of C, H and O are 12, 1 and 16 g mol^ -1 respectively.)
A. 273
Mass of carbon in the compound is calculated from the mass of CO_2 produced: Mass of C = 12 44 mass of CO_2 = 12 44 0.25 = 3 44 g Given that the percentage of carbon in the compound is 25\%: \% of C = Mass of C Total mass X 100 25 = 3 44 X 100 X = 3 44 100 25 = 3 44 4 = 3 11 g X 0.2727 g Verifying this using the percentage of hydrogen: Mass of H = 2 18 mass of H_2O = 2 18 0.12 = 1 75 g \% of H = 1 75 X 100 = 4.89 X = 100 75 4.89 0.2727 g Thus, X = 272.7 10^ -3 g. Rounding to the nearest integer, the required value is 273. Answer: 273
Related: Chemistry — General Organic Chemistry · All PYQ Banks