How much positive and negative charge is there in a cup of water? 

Explanation

Let us assume that the mass of one cup of water is 250 g. The molecular mass of water is 18g. Thus, one mole (`= 6.02 xx 10^23` molecules) of water is 18 g. Therefore the number of molecules in one cup of water is
`(250//18) xx 6.02 xx 10^(23)`
Each molecule of water contains two hydrogen atoms and one oxygen atom, i.e., 10 electrons and 10 protons. Hence the total positive and total negative charge has the same magnitude. It is equal to `(250//18) xx 6.02 xx 10^23 xx 10 xx 1.6 xx 10^(-19)C =1.34 xx10^7C`.