Question

I am confused as to how to solve the below problem. I am not sure which formula to use. At first I thought I calculate the molar mass of NaOH, followed by calculating moles of NaOH. But I don't have the mass of NaOH to calculate moles. Do I convert 10mL to grams to Be able to calculate moles and then the molarity? OR do I use Ci x Vi = Cf x Vf, to solve for the molarity?

If 2.0 ml of 0.010 M of NaOH is mixed with enough water to make the total volume 8mL, what is molarity of the resulting solution?

Answer 1

There are numerous ways to do this but the shortest way is to use the dilution formula that you have in the last sentence of your post.
I even take a short cut with that.
0.01M NaOH x (2.0 mL/8 mL) = ? M.

Note: It isn't needed, but you really do have the mass.
moles NaOH = M x L = ?
Then mols NaOH = grams NaOH/molar mass NaOH.
Knowing mols NaOH and molar mass you can calculate grams.