Question

The mass ratio of copper and oxygen in samples of CuO obtained by different methods were found to be same. This illustrates the:

• A. law of conservation of mass
• B. law of constant proportion
• C. Avogadro's law
• D. law of multiple proportion

Answer 1

The correct option is B law of constant proportion

$\bullet$ Even if the same compound is obtained by different methods, the mass ratio of its constituent elements remains the same.

$\bullet$ For example, the compound CuO can be obtained by the decomposition of ${\text{CuCO}}_3$ or ${\text{Cu(NO}}_3{)}_2$.

$\bullet$ The atomic mass of Cu and O are 64 and 16 respectively.

$\bullet$ However, the mass ratio of copper and oxygen in CuO is 4:1 and is constant irrespective of its source.