Question

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

• A. $1.34 \times 10^{19}\, C$
• B. $1.34 \times 10^{7}\, C$
• C. $2.43 \times 10^{19}\, C$
• D. $2.43 \times 10^{7}\, C$

Answer 1

Answer: (B)

Mass of water $= 250\, g$,
Molecular mass of water $= 18\,g$
Number of molecules in 18 g of water $= 6.02 \times 10^{23}$
Number of molecules in one cup of water $=\frac{250}{18}\times6.02\times10^{23}$
Each molecule of water contains two hydrogen atoms and one oxygen atom, i.e., 10 electrons and 10 protons.
$\therefore $ Total positive charge present in one cup of water
$=\frac{250}{18}\times6.02\times10^{23}\times10\times1.6\times10^{-19}\,C=1.34\times10^{7}\,C$