How would you prepare 250.0 ML of a 0.50 M NaCl Solution

Next time you get a question like this, think about what the final product you want is, and what you have to work with.

You have to assume that you're working with pure NaCl, in which case, you would start with grams.
Then how many grams of NaCl do you need?

For that, you calculate from the end. You need 250.0 mL of 0.50 M, which is 0.50 mols/L,
I want to find out how many grams, but let's find out how many moles we need first, then we can work from there.

You need to translate 250 mL to liters to be able to multiply the two values into a relevant value so,

250 mL = 0.250L,
0.25L x 0.50 mols/L = 0.125 mols

We wanted to find grams needed, correct? So we multiply moles by molecular weight to find grams needed for this solution.

0.125 mols x (58g / 1 mol NaCl) = 7.25 g NaCl

So dissolve 7.25g in 250 mL of water and you get 250mL of 0.50 M NaCl.

weigh out .50/4 = .125 moles of NaCl add water to get 250.0 ml