The charge on 500 cc of water due to protons will be

$\mathrm{V}=500\mathrm{CC};\text{ Mass }=500\times {10}^{-6}{\mathrm{m}}^3\times {10}^3=500\mathrm{g}$
Mass ${\mathrm{H}}_2\mathrm{O}=2+16=18\mathrm{gm}$
No of protons in one  ${\mathrm{H}}_2\mathrm{O}=2+8=10$
$18\mathrm{gm}\text{ (1mole) of }{\mathrm{H}}_2\mathrm{O}\text{ contains }6.023\times {10}^{23} {\mathrm{H}}_2\mathrm{O} \mathrm{molecules}$
500gm contains $=\frac{6.023\times {10}^{23}}{18}\times 500=167.31\times {10}^{23}$ ${\mathrm{H}}_2\mathrm{O} \mathrm{molecules}.$
1 molecule of H₂ O contains 10 protons 

Total charge due to protons$=167.31\times {10}^{23}\times 1.6\times {10}^{-19}\times 10=2.67\times {10}^7\mathrm{C}.$