Question

The no of neutrons in 5g of D2O ?

Answer 1

D20
Atomic mass = 20
no.of neutrons in one molecule = 10

The mass of one deuterium atom is 2(1 p+1 n}

So 20 gm of D2O = 6.023*10^23 D2O molecules.

Now 5 gm of D2O = 1/4*6.023*10^23 D2O molecules= 1.505*10^23 molecules= 1.505*10^23*10 no. of neutrons = 1.505*10^24 no. of neutrons

Answer 2

5g D2O = 0.25 moles
no. of neutrons in one D2O molecule = 10

and 0.25mole = 0.25×6.023×10^23 molecules of D2O
= 1.50575×10^23
so
no of neutrons = 1.50575×10^24