Which of the following has the number of atoms equal to that of 20 g calcium?

Options

A. 12gMg
B. 12gC
C. 24 g Mg
D. 32 g O

Answer

A

Explanation

Molar mass of calcium= 40
20 g calcium= `40/20=5mol`
Molar mass of Mg= 24
`12g Mg=24/12=-5mol`
At NTP, 1 mol of substance contains equal number of molecules.
Hence, numberof atoms in 40 g Ca
= Number of atoms in 12 g Mg