Question

Two gaseous samples of the same compound were analyzed. One contained 1.2 g of carbon and 3.2 g of oxygen. The other contained 27.3% carbon and 72.7% of oxygen. The experimental data follows:

• A. Law of conservation of mass
• B. Law of definite proportion
• C. Law of reciprocal proportion
• D. Law of multiple proportion

Answer 1

Answer: (B)

Law of definite proportion

For the first sample, let's calculate the percentages of carbon and oxygen.

Percentage of carbon $=\frac{massofcarbon}{totalmassofsubstance}\times 100$ $=\frac{1.2}{1.2+3.2}\times 100$ $=\frac{1.2}{4.4}\times 100$ $=27.27$%

Percentage of oxygen $=\frac{massofoxygen}{totalmassofsubstance}\times 100$ $=\frac{3.2}{1.2+3.2}\times 100$ $=\frac{3.2}{4.4}\times 100$ $=72.72$%

For the second sample, the percentages of carbon and oxygen are given:

Percentage of carbon $=27.3$%

Percentage of oxygen $=72.7$%

Both the samples have an equal percentage of the two elements. This follows law of definite proportions: “In a chemical substance the elements are always present in definite proportions by mass”.