Question

Water has a mass per mole of 18.0 g/mol, and each water mo- lecule (H2O) has 10 electrons. (a) How many electrons are there in one liter (1.00 x 10-3 m) of water? (b) What is the net charge of all these electrons?

Answer 1

Answer:

Part 1) Number of electrons in 1 liter of water equals$N=3.346\times 10^{26}$

Part 2) Net charge of all the electrons equals $Charge=53.61\times 10^{6}$

Explanation:

Since we know that the density of water is 1 kilogram per liter thus we infer that mass of 1 liter of water is 1 kilogram hence we need to find electron's in 1 kg of water.

Now since it is given that molar mass of water is 18.0 grams this means that 1 mole of water contains 18 grams of water.

Hence by ratio and proportion number of moles in 1 kg water equals

$n=\frac{1000}{18}$

Now by definition of mole we know that 1 mole of any substance is Avagadro Number of particles.

Hence the no of molecules in 'n' moles of water equals

$n'=\frac{1000}{18}\cdot N_a\\\\n'=\frac{1000}{18}\cdot 6.023\times 10^{23}\\[\tex][tex]\\n'=3.346\times 10^{25}$

Now since it is given that each molecule has 10 electron's thus the total number of electrons in n' molecules equals

$N=10\times 3.346\times 10^{25}\\\\N=3.346\times 10^{26}$

Part 2)

We know that charge of 1 electron equals $1.602\times 10^{-19}C$ the the charge of electrons in 'N' quantity equals

$Charge=1.6022\times 10^{-19}\times 3.346\times 10^{26}\\\\Charge=52.61\times 10^{6}Columbs$