Question

State law of reciprocal proportion with an example.

Answer 1

The law of reciprocal proportions states that “If two different elements combine separately with a fixed mass of a third element, the ratio of the masses in which they do so are either the same as or a simple multiple of the ratio of the masses in which they combine.”

Complete answer:
The law seems to be complicated to understand. For a better understanding, let’s consider an example-
An example is when 3 grams of carbon reacts with 1 gram of hydrogen in order to form methane.
And, when 8 grams of oxygen reacts with 1 gram of hydrogen to form water.
The ratio of their masses i.e mass ratio is C:O = 3:8
In this manner, 12 grams of carbon react with 32 grams of oxygen in order to form carbon dioxide.
The ratio of their masses i.e mass ratio is C:O = 12:32 = 3:8
The mass ratio in which carbon and oxygen combine is similar to the mass ratio in which they combine separately with a fixed mass of H.
When 12 grams of carbon is reacting with 16 grams of oxygen in order to form carbon monoxide
The mass ratio of C:O = 12:16 = 3:4
The ratio of masses in which they react separately has a fixed mass of hydrogen i.e 3:8.
Now, we will find out the ratio of the two ratios i.e $\dfrac{\dfrac{3}{4}}{\dfrac{3}{8}}$= 2:1
So, the ratio in which carbon and oxygen combine is twice the ratio in which they get combined with a fixed mass of hydrogen.

Note:
Jeremias Richter proposed the law of reciprocal proportions, he utilizes the law for neutralization of ratios of metals with the acids. It mentioned that if two substances A and B are reacting chemically with the other substances C and D, then the ratio of the quantities of C and D has the same amount of A as the ratio of the quantities of C and D has with B.