Question

Calculate the number of atoms in each of the following.
i. 52 moles of Argon (Ar).
ii. 52 u of Helium (He).
iii. 52 g of Helium (He).​

Answer 1

Explanation:

(i)  52 moles of Ar

The number of atoms present in 52 mol of Ar can be calculated as follows.

1 moles of Ar = 6.022×1023 atoms of Ar

52 moles of Ar = 52 x 6.022 x 1023

∴ 52 moles of Ar = 3.13144 × 1025

(ii) 52 u of He

The atomic mass of He is 4 amu.

52 u of He will contain  52/4  = 13 atoms

(iii) 52 g of He

1 mole of He = 4 g = 6.022 × 10²³ atoms of He

52 grams of He will contain = 52/4 = 13 moles

Number of atoms in 13 moles of He = 13 × 6.022 × 1023atoms

Number of atoms in 13 moles of He = 78.29× 1023atoms

52 grams of He = 7.829 × 1024 atoms

Answer 2

52 moles of Argon contains 3.131 ×10²⁵ atoms

52u of helium contains 13 atom

52 gm of helium contains 7.83×10²⁴ atoms.

Explanation:

(i) 52 moles of Argon (Ar)

According to the concept of Avogadro's Law

• 1 moles of Argon contains 6.023×10²³

• Given 52 moles of Argon contains X atoms of Argon
• Xatoms =52×6.023×10²³ atoms
• =3.131 ×10²⁵ atoms
• Thus 52 moles of Argon contains 3.131 ×10²⁵ atoms

(ii) 52u of Helium (He)

• Atomic mass of helium =4u
• Given 52u of helium
• which implies that mass of one atom of helium is 4u.
• Thus the number of atoms of Helium contains in 52u=52/4
• it contains 13 atoms
• therefore in 52u of helium contains 13 atom

(iii) Given 52 gm of helium

• Atomic mass of Helium is 4u

• which implies that mass of one atom of helium is 4u.
• Thus the number of atoms of Helium contains in 52u=52/4
• it contains 13 atoms

• The Number of atoms in 52 g of helium will be 13×6.023×10²³
• The Number of atoms=7.83××10²⁴ atoms are present.

• Thus 52 gm of helium contains 7.83×10²⁴ atoms.