Question

Calculate the number of-

I) moles of ammonia molecules in 3.4 g ammonia

ii) atoms of helium in 20g helium

iii) molecules of water in 9.0g of water.​

Answer 1

Answers:-

(i) 0.2 mole

(ii) 3.011×10²⁴ atoms

(iii) 3.011×10²³ molecules

Explanation:-

No of moles in 3.4g Ammonia:-

•Chemical formula of Ammonia - NH₃

Molar mass of Ammonia:-

=>14+1(3)

=>17g

No of moles = Given mass/Molar mass

= 3.4/17

= 0.2 mole

No of atoms in 20g helium:-

•Atomic mass of Helium(H) = 4u

Thus,molar mass of helium is 4g.

•Avogadro number = 6.022×10²³

No of moles in 20g helium:-

= 20/4

= 5 moles

Number of atoms:-

= No of moles×Avogadro number

= 5×6.022×10²³

= 30.11×10²³

= 3.011×10²⁴ atoms

No of molecules in 9.0g of water:-

•Chemical formula of water = H₂O

Molar mass of water:-

= 1(2)+16

= 18g

No of moles in 9.0g or 9g water:-

= 9/18

= 0.5 mole

No of molecules:-

= No of moles×Avogadro number

= 0.5×6.022×10²³

= 3.011×10²³ molecules