Question

It is know that in a sample of water (H2O) there are 3.61 x 10'24 atoms of H. WHAT IS THE MASS IN GRAMS OF THAT SAMPLE

Answer 1

Try this solution:

Given:

N(H)=3.61*10'24;

N(Av)=6.022*10'23;

M(H₂O)=18 (gr/mol).

Calculate: m=?

1) Formula: m=M*ν, where ν=N/N(Av)=[moles], and N(Av) - Avogadro's number.

2) if N(H) is number of atoms, then number of molecules is N(H)/2 (water - H₂O, where 2 atoms of H and 1 atom of O);

3) According to the formula above:

m=M*N(H)/(2N(Av));

m=18*3.61*10'24 / (2*6.022*10'23) ≈ 53.952 (gr.)