A cup contains 250 g of water. Find the total positive charge present in the cup of water.

Mass of water = 250 g, 

Molecular mass of water = 18 g 

Number of molecules in 18 g of water = $6.02 x {10}^{23}$

Number of molecules in one cup of water = $\frac{250}{18}\times 6.02\times {10}^{23}$

Each molecule of water contains two hydrogen atoms and one oxygen atom, i.e., l0 electrons and 10 protons. 

Therefore Total positive charge present in one cup of water

$=\frac{250}{18}\times 6.02\times {10}^{23}\times 10\times 1.6\times {10}^{-19}C=1.34\times {10}^{7}C$