Posted by Bob on Saturday, February 28, 2009 at 9:35pm.
Use the dilution relationship (Mi x Vi = Mf x Vf) to calculate the volume of 0.500 M NaOH needed to prepare 500 mL of .250 M NaOH.
This is my work
? L Solution = 500mL x (1L/1000mL) = .500L
? mol NaOH = .500 L Solution x (0.250 M NaOH/1 L Solution) = .125 mol NaOH
? L solution = .125 mol NaOH x (1L Solution/.500 mol NaOH) = .25
The problem then asks me to round my answer to the nearest ones place, so i have a feeling this equation has an error. Can anyone guide me to getting it right? Thanks!

Chemistry  bobpursley, Saturday, February 28, 2009 at 9:46pm
Why did you shift to liters as the unit of volume. I would have used ml as the volume unit, I suspect that is what the problem intended (but did not say so).

Chemistry  Bob, Saturday, February 28, 2009 at 9:50pm
Aren't you looking for the molarity in this equation. If so, the molarity equation is M = moles of solute / Liters of Solution

Chemistry  DrBob222, Saturday, February 28, 2009 at 9:53pm
You didn't follow the instructions and I don't see that you used MxV= MxV
?? mL x 0.500 M = 500 mL x 0.250 M
?? mL = 500 x 0.250/0.500 = 250 mL.

Chemistry  DrBob222, Saturday, February 28, 2009 at 9:56pm
No, you aren't looking for the molarity. You have molarity of solution 1 and you have molarity of solution 2. You are looking for volume (and you solved for that and obtained 0.250 L which is the same as 250 mL). So I would round my answer to 250 mL.

Chemistry  Bob, Saturday, February 28, 2009 at 10:13pm
Alright, I see my error. I appreciate the help :)
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