Question

One gram mole of a substance contains 6.022 × 10²³ molecules. 

(i) Find out the number of molecules in 2.8 g of nitrogen. 

(ii) Which is the heavier one SO₂ molecule or one CO₂ molecule?

Answer 1

 (i) No. of molecules in1 mole of N₂ = 6.022 × 10²³ 

i.e., No. of molecules in 28 g of N₂ = 6.022 × 10²³ 

∴ No. of molecules in 2.8 g N₂ 

= \(\frac{6.022\times10^{23}}{28}\times 2.8\) = 6.022 x 10²²

(ii) SO₂ is the heavier molecule

Mass of 1 SO₂ molecule  = \(\frac{64}{6.022\times10^{23}}\) = 1.06 x 10^-22 g

Mass of 1 CO₂ molecule = \(\frac{44}{6.022\times10^{23}}\) = 7.31 x 10^-23