Question

Ара.
7. Deduce the number of molecules of
the following compounds in the given
quantities.
Qar
to
As 32g oxygen, 90g water, 8.8g carbon di
oxide, 7.1g chlorine.
​

Answer 1

a. 32 g of oxygen

Number of moles in O2 =  

Mass of O

in grams

Molecular mass of O

 

Mass of O2 in gramsMolecular mass of O2

=  

 

3232 = 1 mol

1 mole of O2 contains 6.022 x 1023 molecules

b. 90 g of water

Number of moles in water =  

Mass of water in grams

Molecular mass of water

 

Mass of water in gramsMolecular mass of water

=  

 

9018 = 5 moles

5 moles of H2O contains-----5 x 6.022 x 1023 molecules = 30.11 x  1023 molecules

C. 8.8 g of CO2

Number of moles in CO2 =  

Mass of CO

in grams

Molecular mass of CO

 

Mass of CO2in gramsMolecular mass of CO2

=  

 

8.844=0.2 mol

0.2 moles of CO2 contains-----0.2 x 6.022 x 1023 molecules = 1.2044 x  1023 molecules

d. 7.1 g of chlorine

No. of moles in chlorine =  

Mass of chlorine in grams

Molecular mass of chlorine

 

Mass of chlorine in gramsMolecular mass of chlorine

=  

 

7.171=0.1 mol

0.1 moles of Cl2 contains-----0.1 x 6.022 x 1023 molecules = 0.6022 x  1023 molecules