Question

Calculate the total number of electrons present in 1.8 g of water.

• A. $N_A$
• B. $N_A/2$
• C. $N_A/10$
• D. $3N_A/10$

Answer 1

The correct option is A $N_A$

1 molecule of water has 2 hydrogens and 1 oxygen atom.

Thus the total number of electrons present in 1 molecule of water is 10. ( 1+1+8)

Since an atomic number of hydrogen is 1 and that of oxygen is 8.

The molecular weight of water is 18. Thus 1.8 g water will have $0.1N_A$ molecules of water and $10\times 0.1N_A=N_A$ electrons.

Hence, the correct option is $A$