Question

total no. of electrons and neutrons in 40g of D2O

Answer 1

for each D no of electron is 1 and neutron number is 1
similarly for each oxygen atom no of electron is 8 as well as neutron is 8 also.
now for each molecule of D2O total no of electron is 1*2+8*1=10 and number of neutron is also 1*2+8*1=10.
i.e. 1 mole D2O≡10 mole electron≡10 mole neutron
now 40g D2O=$\frac{40g(weight taken)}{20g(gram molecular mass of D2O) }$=2mole D2O
i.e. 2 mole D2O ≡ 20 mole electron≡20 mole neutron
so no of electron is 20*6.022*$10^{23}$
the no of neutron is also 20*6.022*$10^{23}$