Atoms, molecules etc a level chem

I can never remember how to calculate each one😭 can somebody please give me equations on how to calculate the number of molecules or number of atoms of a specific element in a given molecule

Reply 1

bl0bf1sh

Original post by Arii256

I can never remember how to calculate each one😭 can somebody please give me equations on how to calculate the number of molecules or number of atoms of a specific element in a given molecule

Do you have an example?

If it's an organic molecule, I generally draw it out (simplified skeletal kind of thing) and count.

Reply 2

Arii256

Original post by bl0bf1sh

Do you have an example?

If it's an organic molecule, I generally draw it out (simplified skeletal kind of thing) and count.

Yeah so like “ what is the number of hydrogen atoms in 0.125 mol of C2H5OH?

Reply 3

bl0bf1sh

Original post by Arii256

Yeah so like “ what is the number of hydrogen atoms in 0.125 mol of C2H5OH?

For something like that I’d use the fact that there are 6.022 x 10^23 units in 1 mole of substance. So you could work out how many molecules of C2H5OH there were and then, as there are 6 H atoms per molecule, multiply that number by 6. :smile: