Question

Match the laws of chemical combinations (in list I) with the examples followed (in list II).

Answer 1

A. Law of conservation of mass: According to this, during any physical or chemical change, the total mass of products remains equal to the total mass of the reactants. So, when $MgC{O}_3$ is heated, following reaction takes place.

$MgC{O}_3\stackrel{△}{\to }MgO+C{O}_2$

$4.2g$ $2.0g$ $2.2g$

So, here as $MassofReactant=MassofProduct$

So, law of conservation of mass is proved.

$A\to 5$

B. Law of Multiple Proportions: According to this, when two elements combine with each other to form two or more than two compounds, the masses of one of the elements which combine with the fixed mass of the other, bear a simple whole number ratio.

So, here as in $S{O}_2$ and $S{O}_3$:

-> In $S{O}_{2}32$ parts by mass of sulphur combine with $32$ parts by mass of oxygen.

-> In $S{O}_3:32$ parts by mass of sulphur combine with $48$ parts by mass of oxygen.

The ratio of masses of oxygen which combine with the fixed mass of sulphur in these compounds is $32:48$ or $2:3$ which is a simple whole number ratio.

$B\to 3$

C. Law of definite proportions: According to this, a chemical compound always contains exactly the same proportion of elements by mass. This, irrespective of the source, a chemical compound always contains the elements in a fixed ratio by mass.

Example: Pure water obtained from river, sea, well etc always contains hydrogen and oxygen combined together in the ratio of $1:8$ by mass

Similarly, $C{H}_4$ has carbon and hydrogen in $3:1$ mass ratio.

(Mass of Carbon is $12grams$ and mass of hydrogen is $1\times 4grams=4grams)$

$C\to 1$

D. Law of reciprocal proportions: According to this law, if two different elements combine separately with the same weight of a third element, the ratio of the masses in which they combine with each other.

Here, in $H_{2}S$ and $S{O}_2$ mass of ratio of $H$ and $O$ with respect to sulphur is $1:6$

$H_{2}S$ $S{O}_2$

$2:32$ $32:32$

$1:16$ $1:1$

Here, hydrogen and oxygen combine with same weight $\left(32g\right)ofthirdelementi.e$S$. So, when hydrogen and oxygen combine, they do so in same or simple multiple of the mass ratio.

$D\to 4$

E. Gay Lussac's law: According to this law, when gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume, provided all gases are at same temperature and pressure.

For example,

$3H_2\left(g\right)+N_2\left(g\right)\to 2N{H}_3\left(g\right)$

$\left(30ml\right)$ $\left(10ml\right)$ $\left(20ml\right)$

Therefore, ratio by volume of nitrogen, hydrogen and ammonia is $1:3:2$ which is a simple whole number ratio.