What is the Law of constant proportions?
The Law of constant proportions states that in a chemical substance, elements are always in a fixed proportion by mass. This is also known as Proust’s Law, named after the French chemist Joseph Proust who was the first one to propose it.
To understand this law, consider the reaction of 2 elements, A and B to give a compound C. In this reaction, 2 units of A react with 3 units of B to give 1 unit of C. Even if one atom from any of these units is removed or added, then it can no longer be called compound C.
This means that the number of atoms in C is fixed and has a constant mass according to the law of constant proportions.
Law of constant proportions
Examples of law of constant proportions
– In chemistry
When ammonia is decomposed by extreme heat or some other way, we get the nitrogen and hydrogen atoms in the same proportions by mass.
If we decompose 17 grams of ammonia, we will always get 14 grams of nitrogen and 3 grams of hydrogen. There is a constant ratio of 14:3 between nitrogen and hydrogen present in ammonia.
Example of ammonia
– In real life
To make 1 chocolate milk, we mix milk, sugar and chocolate in a specific proportion. And for preparing milkshakes for 10 people, we will increase the quantity of ingredients equivalently, that is 10 times. This will ensure that the milkshake tastes the same for 10 people as well.
