<p>Yes, this is homework, but it's not for a grade and we ran out of time in class, and I'm somewhat unsure of where to begin. Help would be appreciated.</p>
<p>Question: How much water should be a dded to 500 ml of a solution of HCL with a pH of 2.00 to bring the pH to 2.50?</p>
<p>pH 2 means the concentration of H+ is 10^-2 M.
to find the moles of H+, times the volume and concentration, ie.
moles = 0.5 L x 10^-2 M = 0.005 moles</p>
<p>pH 2.5 means the concentration of H+ is 10^-2.5 = 3.16e-3M
concentration = moles/volume
volume = moles / concentration
= 0.005 moles / 3.16e-3 M
= 1.581 L
= 1581 mL
you need to add 1081 mL of water.</p>