Question

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

Answer 1

Step 1: Calculate the total number of molecules

The chemical composition of water is $H_{2}O$.

Oxygen has a molecular mass $16$ and hydrogen has a molecular mass $1$.

Hence, the total molecular mass of water is $16+2\times 1=18$

Therefore, $1mol$ of water is equivalent to $18g$ of water.

We know that the number of water molecules in each mole of water is $6.023\times {10}^{23}$.

Hence, the number of water molecules in $250g$ of water $=\frac{6.023\times {10}^{23}}{18}\times 250$ molecules

Step 2: Calculate the total positive charge

The atomic number of hydrogen is $1$ and that of oxygen is $8$.

Therefore, the total number of electrons or protons present in one molecule of water is

$2\times 1+8=10$

Therefore, the total number of electrons or protons in $250g$ of water $=\frac{6.023\times {10}^{23}}{18}\times 250\times 10$

We know that charge of one electron or proton is $1.6\times {10}^{-19}C$.

Hence, the total positive charge present in the cup of water

$=\frac{6.023\times {10}^{23}}{18}\times 250\times 10\times 1.6\times {10}^{-19}$

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

Hence, the total positive charge is $250g$ of water is $1.34\times {10}^{7}C$.