A solution is made by dilution 400.mL of 2.0 M HCL to a final volume of 1000. mL. what is the pH of this solution? i'm stuck on this question i have no idea what to do, can anyone help? thanks:)

Answer 1

The easy way to do this problem is:
Starting with 2.0 M, you dilute it from 400 to 1000 mL; therefore, the final concentration is no other than
2.0 x (400/1000) = 0.80 M

The harder way, but the one you've been taught to rely on, ALWAYS, is to use mols (because everything works in mols in chemistry).
How many mols do you have to start with? That is mols = M x L = 2.0 x 0.400 =0.80 mols.
How many mols will you have after it is diluted? Of course, you will have 0.80 mols.
What is the concentration now in mols/L (which of course is molarity) = 0.80/1.0 L = 0.80 mol/L = 0.8 M.