How many moles of Br are there in 35.7 grams of Br?

Answer 1

Basically you want to use the molar mass of bromine to find how many moles are in 35.7 grams of Br. The molar mass has the units grams/mole. So to cancel out grams and end up with moles you want to divide our given grams by the molar mass. The molar mass can be found on the periodic table.

(35.7 g Br) / (79.904 g/mole) = .447 moles Br

Your number might be a little bit different depending on the periodic table you are using, and also be sure to keep it to three significant figures!