Question

what is a mole and why does a mole of magnesium and a mole of carbon weigh different they have the same number of atoms?

Answer 1

~ A mole is a unit of 6*10^23.

~One mole of carbon atoms has a mass of exactly 12 g.

~ Because magnesium atoms each have twice the mass of carbon atoms ( 24Mg compared with 12C), one mole of magnesium has a mass of 24 g.

~ Rather, one mole of any element has a mass in grams that is equal to its relative atomic mass.