How do I set this problem up?

Question

I need to make up 2.5L of a 1.25M solution of NaCl for next lab. How many moles of NaCl do I need? and how many grams of NaCl do I need?

Answer 1

First things first: Molecular weight Na = 22.99, Cl = 35.45.
NaCl = 58.44.

You'll need n=mv/1000
= 1.25 x 2500/1000
= 3.125 moles

3.125 x 58.44 = 182.625g of NaCl

Answer 2

To find moles Moles= Volume x molarity.
So you have 2.5 L x 1.25 M = 3.75 moles.
Multiply moles by mole wt of salt to get grams.