Question

What is the mass of water if it contains 6.022 x 10²⁵ atoms of oxygen

Answer 1

Molecular formula for water is $H_2O$

Mass of oxygen =16g which is equivalent to $6.022\times10^{25}atoms$

Atoms of hydrogen $=2/16\times6.022\times 10^{25}=7.5275\times 10^{24} atoms$

Total atoms in water $=6.022\times 10^{25} +7.5275\times 10^{24}=6.77475\times 10^{25}atoms$

Avogadro's number = $6.022\times 10^{23}$

Mass of water $=\frac{6.77475\times 10^{25}}{6.022\times 10^{23}}=112.5g$