Question

Deduce the number of molecules of the following compounds in the given quantities.
32g oxygen, 90g water, 8.8g carbon dioxide, 7.1g 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.

Answer 2

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