Question

A cup contains 250 g of water. Find the number of positive charges 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)

$1.34 \times 10^{7}C$

Answer 2

: Mass of water = 250 g molecular mass of water = 18 g Number of molecules in 18 g of water (Avogadro’s Number)= $6.02 \times 10^{23}$ $\therefore$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., 10 electrons and 10 protons. $\therefore$Total positive and negative charge has the same magnitude and is

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

$= 1.34 \times 10^{7}C$