How many moles of ${\text{CaCO}}_3$ are present in 500 g of ${\text{CaCO}}_3$?
Gram atomic masses Ca, C, and O are 40, 12, and 16 respectively.

The correct option is A 5

Given mass of ${\text{CaCO}}_3$ = 500 g
Gram molecular mass of ${\text{CaCO}}_3$ =
Atomic mass of Ca + Atomic mass of C + 3 $\times$ Atomic mass of O = 40 + 12 + 3 $\times$ 16 = 100 g

We know that, number of moles
= $\frac{\text{Given mass}}{\text{Gram molecular mass}}$

After inserting the given values in the above equation we have, moles of ${\text{CaCO}}_3$ = $\frac{500}{100}$ = 5 moles

Therefore, number of moles present in 500 g of ${\text{CaCO}}_3$ is 5.