Question

Calculate the number of moles in 

(i) 12.046 × 10²³ atoms of copper 

(ii) 27.95 g of iron 

(iii) 1.51 × 10²³ molecules of CO₂

Answer 1

(i) 12.046 × 10²³ atoms of copper 

6.023 × 10²³ atoms of copper = 1 mole 

12.046 × 10²³ atoms of copper = \(\frac{1\times12.046\times10^{23}}{6.023\times10^{23}}\)= 2 moles of copper 

(ii) 27.95 g of iron 

55.9 g of iron = 1 mole 

27.95 g of iron =  \(\frac{1}{55.9}\) x 27.95 = 0.5 mole of iron. 

(iii) 1.51 × 10²³ molecules of CO₂

No of mole = \(\frac{No.\,of\,molecules}{A\,vogadro\,number}\)

= \(\frac{1.51\times10^{23}}{6.023\times10^{23}}\)

= 0.25 mole of CO₂