Question

How to express 20 g of CO₂ in moles. (Atomic mass C = 12, O = 16)
1. 4 mole
2. 2 mole
3. 1 mole
4. 0.45 moles 

Answer 1

Correct Answer - Option 4 : 0.45 moles 

The correct answer is 0.45 moles.

The number of moles of a substance in a given sample can be represented by the following formula:
n = m/M
Here, n = the number of moles of the substance 
           m = mass of the given substance
           M= Molar mass
Given- Atomic mass of C= 12
           The atomic mass of O= 16
Molar mass of 1 mole of CO₂ = Molar mass of C +2 x Molar mass of O 
                                                    = 12 + 32 = 44
So, no. of moles in 20 gm of CO₂ = 20/44 moles of CO₂
                                                        =  0.45 moles