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Question
Estimate the number of electrons in 100 g of water. How much is the total negative charge on these electrons?
Solution
Molecular mass of water= 18 g
Number of molecules in 18 g of H2O = Avogadro's number
= 6.023 × 1023
Number of electrons in 1 molecule of H2O = (2 × 1) + 8 = 10
Number of electrons in 6.023 × 1023 molecules of H2O = 6.023 × 1024
That is, number of electrons in 18 g of H2O = 6.023 × 1024
So, number of electrons in 100 g of H2O = \[\frac{6 . 023 \times {10}^{24}}{18} \times 100\]
= 3.34 × 1025
∴ Total charge = 3.34 × 1025 × 1.6 × 10−19
= 5.34 × 106 C
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