What is the mass of 2.5 moles of BeCl2?

Question

What formula do I need to use to find the mass?

Answer 1

in order to convert the moles over into the mass you want to multiply by the Molar Mass!

on this one that means taking

2.5 mol x (79.918 g/mol) = 199.785 g

meaning that the mass of 2.5 moles is approximately 199.8 grams

Answer 2

First you find the molar mass of each atom in your periodic table:

Beryllium has 9.01 g/mol and Chlorine has 34.45 g/mol.

Since the molecule is BeCl2, you have to add the molar masses of 1 BE + 2 Cl, which makes 9.01g/mol + 2(34.45g/mol) = 77.91g/mol.

Since you have 2.5 mol of the substance, you have to multiply 77.91g/mol with 2.5mol and get 194.78g.