Question

Deduce the number of molecules of the following compounds in the given quantities. (a) 8 gm of Oxygen (b) 27 gm of Water (c) 71 gm of Chlorine ​

Answer 1

For Oxygen,  

Mass = 32 g.

Molar Mass = 32 g.  

∵ No. of molecules = Mass/Molar Mass × Avogadro's number.  

∴ No. of molecules = 32/32 × 6.022 × 10²³

   = 6.022 × 10²³ molecules.  

For Water,  

Mass = 90 g.

Molar mass = 18 g.

∴ No. of molecules = 90/18 × 6.022 × 10²³

  = 5 × 6.022 × 10²³

  = 3.011 × 10²⁴ molecules.  

For Carbon dioxide,  

Mass = 8.8 g.

Molar mass = 44 g.  

∴  No. of molecules = 8.8/44 × 6.022 × 10²³

   1.2044 × 10²³ molecules.  

For Chlorine,  

Mass = 7.1 g.

Molar Mass = 71 g.  

∴ No. of molecules = 7.1/71 ×  6.022 × 10²³

  =  6.022 × 10²² molecules.

Hope it helps.