How many grams would you weigh out on an electronic balance if a reaction requires 4.5 moles of lithium oxide?
This means that 1 mole of Li is 7grams and 1 mole of O is 16grams.
Together, they have a combined molecular weight of:
7+16= 23 grams per mole (or g/mol as you'll often see it written)
So, now that you know there are 23 grams in one mole of lithium oxide, you can simply multiply it by the number of moles you need: