We have to calculate the number of coulombs of positive charge in a glass of water. We may assume that the volume of water in the glass is .

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Mass of of water will be 250 g. Amount of positive charge in each molecule of water, , is , as number of protons in a molecule are 2+8.

The number of molecules in 18 g of water are equal to the Avogadro’s number, . Therefore, the number of molecules in 250 g of water will be

Therefore, the total positive charge in coulombs in of water will be