Question

A sample of baking soda, naHCO3, always contains 27.37% by mass of sodium, 1.20% of hydrogen, 14.30% of carbon, and 57.14% of oxygen.
Which law do these data illustrate? State the law.

Answer 1

Answer: Law of definite proportion.

Explanation: Law of definite proportion states that any chemical compound consists of elements in a fixed ratio by their masses. This law is also known as Proust's Law.

We are given a chemical compound $NaHCO_3$

Assuming that the total mass of 1 mole of $NaHCO_3$ = 100 grams

where

Mass of Sodium = 27.37 grams

Mass of Hydrogen =  1.20 grams

Mass of Carbon = 14.30 grams

Mass of Oxygen = 57.14 grams

To Calculate the ratio of all the elements, we divide each of the masses by the lowest mass.

$\text{Mass ratio of Sodium}=\frac{27.37}{1.20}=22.80\approx 23$

$\text{Mass ratio of Hydrogen}=\frac{1.20}{1.20}=1$

$\text{Mass ratio of Carbon}=\frac{14.30}{1.20}=11.91\approx 12$

$\text{Mass ratio of Oxygen}=\frac{57.14}{1.20}=47.61\approx 48$

Mass ratio of elements in $NaHCO_3=Sodium:Hydrogen:Carbon:Oxygen$

Na : H : C : O = 23 : 1 : 12 : 48

For every $NaHCO_3$ compound, this mass ratio will always be constant.