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

MCQ

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

#### Options

• $\ce{4 g He}$

• $\ce{46 g Na}$

• $\ce{0.40 g Ca}$

• $\ce{12 g He}$

#### Solution

$\ce{12 g He}$

Explanation:

(A) The number of moles is given by the following formula,

Moles = "Mass"/"Molar mass"  .......(1)

The number of moles of He is calculated by using equation (1) as follows,

Moles of O2 = ( 4 g)/((4 g)/(mol) = 1 mol

The number of atoms can be calculated as, number of moles = "Numbers of atoms"/"Avogadro's number"  .......(2)

On substituting the values in the above equation:

1 mol = "Number of atoms"/(6.022 xx 100^23)

Number of atoms = 1 xx 6.022 xx 10^23

(B) The number of moles of Na is calculated by using equation (1) as follows,

Moles of Na = (46 g)/((23 g)/(mol) = 2 mol

The number of atoms can be calculated by using equation (2) as follows,

2 mol = "Number of atoms"/(6.022 xx 10^23)

Number of atoms = 2 xx 6.022 xx 10^23

(C) The number of moles Ca is calculated by using equation (1) as follows,

Moles of Ca = (0.40 g)/((40 g)/(mol) = 0.01 mol

The number of atoms can be calculated by using equation (2) as follows,

0.01 mol = "Number of atoms"/(6.022 xx 10^23)

Number of atoms = 0.01 xx 6.022 xx 10^23

(D) The number of moles of He is calculated by using equation (1) as follows,

Moles of He = (12 g)/((4 g)/(mol) = 3 mol

The number of atoms can be calculated by using equation (2) as follows,

3 mil = "Number of atoms"/(6.022 xx 10^23)

Number of atoms = 3 xx 6.022 xx 10^23

Thus, 12 g He contains the highest number of atoms.

Is there an error in this question or solution?
Chapter 1: Some Basic Concepts of Chemistry - Multiple Choice Questions (Type - I) [Page 2]

#### APPEARS IN

NCERT Exemplar Chemistry Class 11
Chapter 1 Some Basic Concepts of Chemistry
Multiple Choice Questions (Type - I) | Q 5 | Page 2

Share