Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: chmdummy1982 on February 28, 2009, 11:10:37 PM
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I am having trouble with a couple of chemistry problems. One I was able to answer half of, and the other I don't even know how to start. Any help would be greatly appreciated!
Question 1
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 0.250 M NaOH.
? mL x .500 M NaOH = (500mL x.250M)/.500 = 250 mL
Now here is where I am lost with this problem:
What volume of water would you add to the 0.500 M NaOH volume calculated aove to actually make 500 mL of 0.250 M NaOH?
Question 2
49.22 mL of a 2.01 M NaOH solution reacts completely with 40.28 mL of HCl solution according to the balanced chemical reaction shown below:
HCl (aq) + NaOH(ap) -> NaCl(aq) + H2O(i)
How many moles of HCl reacted?
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What volume of water would you add to the 0.500 M NaOH volume calculated aove to actually make 500 mL of 0.250 M NaOH?
You have calculated it! 250mL
How many moles of HCl reacted?
Check this out, one of this forum admin's website: http://www.chembuddy.com/?left=balancing-stoichiometry&right=ratio-proportions
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So heres my work.
(40.28 / 49.22) x 2.01 = 986.3590 (thousandths place)
would this be correct?
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Nope, they are asking for moles of HCl reacted. How do you calculate moles? Any formula you known of that could be apply to this question?
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Would the molarity formula have anything to do with it?
M = moles of solute/Liters of solution
I'll give it another shot..
(49.22 x 2.01)/40.28 = 2.4561
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M = moles of solute/Liters of solution
I'll give it another shot..
(49.22 x 2.01)/40.28 = 2.4561
Formula correct, working wrong. What you are calculating is molarity but they are asking for moles.
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Would I have to use this equation??
moles = M X V?
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Yes