Question

Calculate the total number of electron present in 3.2 g of oxygen gas?

Answer 1

Molar mass of O2 = 32g
​No of moles in 3.2 g O2 =
3.2
32
= 0.1 mol
No of oxygen molecules = 0.1
×
6.022×
1023
No of electrons in one molecule of O2 = 8
×
2=16
No of electrons in ​0.1
×
6.022
×
1023 molecules = ​0.1
×6.022×1023
×
16 = 9.6352
×
1​023 electrons

Answer 2

Given: Mass of Oxygen gas - m = 3.2g

To Find: Number of electrons present in 3.2g of oxygen gas

              Number of molecules of O₂

Solution:

The atomic number of Oxygen = 8

Atomic number = number of electrons present in the atom.

Number of electrons present in 1 O₂ molecule = 8 × 2 = 16 electrons.

To find the number of electrons in 3.2g of oxygen gas, first, find the number of molecules of O₂.

Formula used:

Number of moles of O₂ = Given mass(m)/ Molecular mass(M)

Also, Number of moles = the given number of molecules(N)/Avagadro's number Nₐ,

where Nₐ = 6.023 × 10²³ molecules

Hence m/M  = N/Nₐ

∴N = m × Nₐ/ M (m = 3.3g, M = 16 × 2 = 32g)

Applying the above formula:

N = 3.2 × 6.023 × 10²³/ 32

N = 32/10 × 6.023/32 × 10²³

N = 6.023 × 10²³/10

N = 6.023 × 10²² molecules of O₂

1 molecule of O₂ = 16 electrons

6.023 × 10²² molecules of O₂ = 16 ×  6.023 × 10²²

                                            = 9.63 × 10²³electrons

Hence, 9.63 × 10²³electrons are present in 3.2 g of oxygen gas.