Question

no. of neutrons in 5 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