MHTCET 11 May 2024 Shift 1 Paper

Concept:The law of multiple proportion applies only when two same elements form two or more different compounds.Explanation:In $\mathrm{NO}$ and $\mathrm{NO}_{2}$, the same elements nitrogen and oxygen combine in different ratios.For a fixed mass of nitrogen, the masses of oxygen are in the simple whole-number ratio $1:2$.So, option A follows the law.Similarly, $\mathrm{CO}$ and $\mathrm{CO}_{2}$ are compounds of carbon and oxygen.For a fixed mass of carbon, the oxygen masses are in the ratio $1:2$.So, option B follows the law.Likewise, $\mathrm{H}_{2}\mathrm{O}$ and $\mathrm{H}_{2}\mathrm{O}_{2}$ are compounds of hydrogen and oxygen.For a fixed mass of hydrogen, the oxygen masses are in the ratio $1:2$.So, option C follows the law.In $\mathrm{Na}_{2}\mathrm{S}$ and $\mathrm{NaF}$, the second elements are different: sulfur and fluorine.They are not compounds formed by the same pair of elements.Hence, the law of multiple proportion cannot be demonstrated by this pair.Answer:Option D: $\mathrm{Na}_{2}\mathrm{S}, \mathrm{NaF}$