Suppose all the electrons of 100 g water are lumped together to form a negatively charged particle and all the nuclei are lumped together to form a positively charged particle. If these two particle are placed 10.0 cm away from each other, find the force of attraction between them. Compare it with your weight.

Sol. Molecular weight of H base 2O = 2 × 1 × 16 = 16 No. of electrons present in one molecule of H base 2O = 10 18 gm of H base 2O has 6.023 × 10^23 molecule 18 gm of H base 2O has 6.023 × 10^23 × 10 electrons 100 gm of H base 2O has 6.023 * 10^24/18 * 100 elecrons So number of protons = 6.023 * 10^26/18 protons (since atom is electrically neutral) Charge of protons = 1.6 * 10^-19 * 6.023 * 10^26/18 coulomb = 1.6 * 6.023 * 10^7/18 coulomb Charge of electrons = = 1.6 * 6.023 * 10^7/18 coulomb Hence Electrical force = 9 * 10^9(1.6 * 6.023 * 10^7/18)*( 1.6 * 6.023 * 10^7/18)/(10 * 10^-2)^2 = 8 * 6.023/18 * 1.6 * 6.023 * 10^25 = 2.56 * 10^25 Newton