Question

What weight of calcium contains the same number of atoms as those in $3g$ of carbon?

• A. $10g$
• B. $20g$
• C. $30g$
• D. $40g$

Answer 1

The correct option is A $10g$

Atomic weights of $C$ and $Ca$ are 12 g/mol and 40 g/mol respectively.

3 g $C=\frac{3g}{12g/mol}=0.25molC$.

Number of moles of $Ca=$ number of moles of $C=$ 0.25.
Weight of $Ca=3mol\times 40g/mol=10g$.
Note: Since $C$ and $Ca$ samples have same number of atoms, they will have same number of moles.