Question

The number of molecules in 18mg of water in terms of Avogadro number N is​

Answer 1

Answer:

weight of water =18 mg=18×10  

−3

g

∴ Number of moles =  

Molar mass

Weight

​

 

                                 =  

18

18×10  

−3

 

​

=1×10  

−3

 moles

Number of molecules = Number of moles × Avogadro number

                                    =1×10  

−3

×N  

                                    =10  

−3

 N.

Explanation:

Answer 2

Explanation:

Answer

Correct option is

A

10

−3

N

Given, weight of water =18 mg=18×10

−3

g

∴ Number of moles =

Molar mass

Weight

=

18

18×10

−3

=1×10

−3

moles

Number of molecules = Number of moles × Avogadro number

=1×10

−3

×N

=10

−3

N.

Hence, option A is correct