Posted by Andy on Sunday, March 20, 2011 at 11:46am.
These are best done by making an ICE chart.
1L x 0.42M HCl = 0.42 moles HCl
NaOH = 0.13 moles added.
...........HCl + NaOH ==> NaCl + H2O
begin......0.42...0.........0......0
add..............0.13................
react....-0.13..-0.13....+0.13...+0.13
final......0.29....0.......-.13...0.13
You can see that you have 0.29 mole HCl and it's in 1L soln; therefore, HCl being a strong acid (100% ionized), the (H3O^+) = (HCl) = 0.29moles/L = 0.29M.
The second one is done the same way except that the NaOH will be in excess. After you find the (OH^-), convert to (H3O^+) by (H3O^+)(OH^-) = Kw = 1E-14
thank you very much
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