Question

52 u of He contains :
a.) $(4 \times 6.023 \times {10^{23}})$ atom
b.) 13 atoms
c.) $(13 \times 6.023 \times {10^{23}})$ atoms
d.) 4 atoms

Answer 1

Hint:. From the given mass, we can find the number of moles of Helium. The formula to find number of moles is as -
Number of moles = $\dfrac{{Given{\text{ }}mass}}{{Molar{\text{ mass}}}}$
We know that one mole of an element contains $6.023 \times {10^{23}}$ atoms. So, multiplication with $6.023 \times {10^{23}}$ will give a number of atoms.

Complete step by step answer:
First, we will find the number of moles of He atoms present as -
We have been given Molar mass of He = 52 u
We know that Molar mass of He = 4 u
Number of moles = $\dfrac{{Given{\text{ }}mass}}{{Molar{\text{ mass}}}}$
Number of moles = $\dfrac{{52}}{4}$
Number of moles = 13 moles
Further, we have that 1 mole of an atom contains $6.023 \times {10^{23}}$ atoms
Thus, 13 moles of He = $(13 \times 6.023 \times {10^{23}})$ atoms
So, the correct answer is “Option C”.

Note: The mole is a quantity. It is one of fundamental units which is used. It is used to represent the amount of a substance in a chemical reaction. The unit is mole or mol.
A mole can be defined as the mass of the substance equal to the quantity of its basic units. This basic unit can be volume, number of atoms, molecules or ions. For example - one mole of an atom has $6.023 \times {10^{23}}$ number of atoms, molecules if it is a compound, ions if ionic species and this value is equal to 22.4 L of gas at STP.