The number of atoms present in one mole of an element is equal to Avogadro number. Which of the following elements contains the greatest number of atoms ?

Options

A. `4" g He"`
B. 46 g Na
C. `0.4` g Ca
D. 12 g He

Answer

D

Explanation

For comparing number of atoms, first we calculate the
moles as all are monoatomic and hence,
Number of moles `=("Mass")/("Atomic mass")`
Moles of 4 g He `=4/4 = 1` mol
46 g Na `=46/23 =2` mol
`0.40` g Ca `=(0.40)/40=0.01` mol
12 g He `= 12/4=3` mol
Now, number of atoms `="moles"xx"N"_("A")`
Therefore, number of atoms are highest in 12 g He as it has the
Masimum number of moles.