Question

The relative formula mass, ${M_r}$, of calcium carbonate, $CaC{O_3}$, is $100$. What is the mass of carbon present in $100{\text{ }}g$ of calcium carbonate?
A. $12g$
B. $36g$
C. $40g$
D. $60g$

Answer 1

Relative formula mass also denoted by ${M_r}$ is defined as the sum of the relative atomic masses of the atoms present in the formula.

Complete answer:
Now, as we are given $100g$ of $CaC{O_3}$ and we are required to calculate the mass of carbon present first we will see the number of carbon atoms present in the formula, which is $1$. Now, the mass of $1$ mole of carbon as we know is $12g$ and multiplying it by one we get $12g$. Hence, $12g$ of carbon is present in $100g$ of $CaC{O_3}$.
So, the correct answer is Option A.

Additional Information:
Let us know about $CaC{O_3}$ also called as calcium carbonate, It is a common chemical and is found in rocks in the form of minerals, for example, limestone which is a type of sedimentary rock of calcite, and is one of the main components of pearls and also found in shells of water living organisms. Calcium carbonate has an agricultural use as it is one of the main Ingredients in agricultural lime, and is created when calcium ions react with carbonate ions present in hard water to produce limescale. Medically, it is used as a supplement of calcium and used as an antacid as well, but excessive consumption of it can be hazardous and can cause poor digestion.

Note:
Ionic molecules do not exist as a molecule but their relative formula mass can be calculated easily in the same way as we calculate for other chemical species, as shown for calcium carbonate.