Q. 18

# Which of the following pairs have the same number of atoms?

A. 16 g of O_{2} (g) and 4 g of H_{2} (g)

B. 16 g of O_{2} and 44 g of CO_{2}

C. 28 g of N_{2} and 32 g of O_{2}

D. 12 g of C(s) and 23 g of Na(s)

Answer :

One mole of a substance is the mass of a substance which contains exactly 6.023 x 10^{23} molecules or atoms of that substance. So if two different substances are one mole each, they contain the same number of atoms.

The atomic masses of the given substances are as follows: O = 16, H = 1, CO_{2} = 44, N = 14, C = 12, Na = 23.

The number of atoms present in each mass is given by the formula

For option (i), No. of oxygen atoms = x 6.023 x 10^{23}

No. of hydrogen atoms = x 6.023 x 10^{23}

(ii) No. of oxygen atoms = x 6.023 x 10^{23}

No. of carbon dioxide atoms = x 6.023 x 10^{23}

(iii) No. of nitrogen atoms = x 6.023 x 10^{23}

No. of oxygen atoms = x 6.023 x 10^{23}

D. No. of carbon atoms = x 6.023 x 10^{23}

No. of sodium atoms = x 6.023 x 10^{23}

According to the calculation, the correct answers are (ii), (iii), and (iv).

Rate this question :

Calculate the number of atoms in each of the following:

(i) 52 moles of Ar

(ii) 52 u of He

(iii) 52 g of He.

NCERT - Chemistry Part-IWhat will be the mass of one ^{12}C atom in g?

How much copper can be obtained from 100 g of copper sulphate (CuSO_{4})?