Name: Law of Multiple Proportions
Uploaded: 2019-07-19
Duration: 6 min 43 s
Description: The Law of multiple proportions is applicable only when two elements combine to form two or more compounds. Watch this video to know how this law is applicable.

Question

Phosphorus trichloride contains

22.57

% of phosphorus, phosphine (

{PH}_{3}

) contains

91.18

% of phosphorus while hydrogen chloride gas contains

97.23

% of chlorine. Prove by calculations, which law is illustrated by these data.

Accepted Answer

In phosphorus trichloride ( ${PCl}_{3}$ )

Weight of phosphorus $= 22.57 g$

Weight of chlorine $= 100 - 22.57 = 77.43 g$

Hence, $22.57 g$ of phosphorus combines with $77.43 g$ chlorine.

Therefore, $1 g$ of phosphorus combines with chlorine $= \frac{77.43}{22.57} = 3.43 g$

In phosphine ( ${PH}_{3}$ )

Weight of phosphorus $= 91.18 g$

Weight of hydrogen $= 100 - 91.18 = 8.82 g$

Hence, $91.18 g$ of phosphorus have combined with hydrogen $= 8.82 g$

Therefore, $1 g$ of phosphorus has combined with hydrogen $= \frac{8.82}{91.98} = 0.097 g$

Thus, the ratios by weights of chlorine and hydrogen combining with a fixed weight of phosphorus in the two compounds is $3.43 : 0.097$ (This ratio is not the same) ....(i)

In hydrochloric acid gas ( $HCl$ ),
Weight of chlorine $= 97.23 g$

Weight of hydrogen $= 100 - 97.23 = 2.77 g$

Thus, chlorine and hydrogen have combined in the ratio $97.23 : 2.77$ ....(ii)

Let us compare the two ratios.

These are related to each other as $= \frac{3.43}{0.097} : \frac{97.23}{2.77}$ $= 35.37 : 35.10$ or $1 : 1$ (approximately). The data is according to the Law of Reciprocal Proportions.

Phosphorus trichloride contains $22.57$ % of phosphorus, phosphine ( ${PH}_{3}$ ) contains $91.18$ % of phosphorus while hydrogen chloride gas contains $97.23$ % of chlorine. Prove by calculations, which law is illustrated by these data.

Important Questions on Some Basic Concepts of Chemistry

Learn and Prepare for any exam you want !

Phosphorus trichloride contains 22.57% of phosphorus, phosphine (PH3 ) contains 91.18 % of phosphorus while hydrogen chloride gas contains 97.23% of chlorine. Prove by calculations, which law is illustrated by these data.

Important Questions on Some Basic Concepts of Chemistry

Learn and Prepare for any exam you want !

Phosphorus trichloride contains $22.57$ % of phosphorus, phosphine ( ${PH}_{3}$ ) contains $91.18$ % of phosphorus while hydrogen chloride gas contains $97.23$ % of chlorine. Prove by calculations, which law is illustrated by these data.