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:

a) There are $3,35*10^{26}$ electrons in a liter of water.

b) The net charge is -53601707,1 C

Explanation:

a) To find out how many electrons are in a liter of water (equivalent to 1000 grams of water), we have to find out how many molecules of water there are and then multiply it by 10 (e- per molecule).

We can find out how many molecules are by finding the number of moles and then multiplying it by Avogadro's number (number of elements per mol):

$e^{-}= \frac{m_{water} }{M_{water} } * Avogadro* \frac{e^{-} }{molecule}=  \frac{1000g }{18g/mol} * 6,022*10^{23} * \frac{10e^{-} }{molecule}=3,35*10^{26} e^{-}$

b) As all electrons have the same charge, in order to find the net charge of those electrons we have to multiply the charge of a single electron by the number of electrons:

$Net charge= -1,602*10^{-19}  \frac{C}{e^{-} }  *3,35*10^{26} e^{-}=-53601707,1 C$

An important clarification is that while the net charge may seem huge, water as a whole is a neutral medium, because there are as many protons as there are electrons, and as they have the same charge, the net charge of water is 0.