Question

2*10^3 water molecules are removed from 36g of water. calculate the no. of hydrogen atoms present in the remaining sample of water

Answer 1

So,
36g of H2O i.e. 2 moles of h2o
So no. Of molecules of h2o are (6.022*10^23)*2= 12.044*10^23
Now 2000 molecules are removed
12.044*10^23- 2000=12.044*10^23(approx.)
So no. Of h atoms in 12.044*10^23 molecules =2*12.044*10^23=24.088*10^23(as 2 h atoms in 1 h2o molecule)
Hope u understood...