Chemistry

How many electrons are there in the average bowl of cereal?

Well typically breakfast consists of around 200 grams of cereal and roughly 200 millilitres of milk. For these purposes I will make some assumptions:

First assume that the cereal is made up completely of carbon. 12 grams of carbon contains approximately 6.023 x 1023 atoms of carbon (The Avogadro Number from earlier on).  So 200 grams of carbon contains (200/12) ~ 17 x 6.023 x 1023 atoms. Each atom of carbon contains 6 electrons. So the final total is 6 x 17 x 6.023 x 1023 which comes to 6.14 x 1025 atoms.

Next assume that the milk is made up completely of water. 18 grams of water contains approximately 6.023 x 1023 molecules of water (The Avogadro Number again). So 200 grams of water contains (200/18) ~ 11 x 6.023 x 1023 atoms. Each molecule of water contains 2 atoms of hydrogen each with 1 electron and 1 atom of oxygen each with 8 electrons which makes 10 electrons per molecule. . So the final total is 10 x 11 x 6.023 x 1023 which comes to 6.63 x 1025

These two numbers are so similar that it barely makes any difference what we assume – so 400 g of cereal – made up of any mix of milk/cereal contains roughly 6.14 x 1025 + 6.63 x 1025 ~ 1.27 x 1026 electrons.

And pretty much exactly the same number of protons.