ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: sin0001 on September 19, 2012, 10:02:56 pm
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20 mL slutions of 0.1M concentration of Sulfuric acid, Nitric acid and Ethanoic acid are seperately titrated with 0.1M of NaOH. In order to react completely:
A: all three acids would require the same amount of NaOH
B: Nitric acid woud require more NaOH than ethanoic acid but less than Sulfuric acid
C: Sulfuric acid and Nitric acid would require the same amount of NaOH but ethanoic acid would require less
D: Ethanoic acid and Nitric acid would require the same amount of NaOH, but sulfuric acid would require more
The answer is D, but can someone explain why ethanoic acid and nitric acid require the same amount, i get that they are monoprotic acids and sulfuric acid is diprotic, but in reality, ethanoic acid and nitric acid of same concentration would produce very different amounts of H+ ions, because of their different Ka values and they would ionise to different extents. Isn't the NaOH reacting with the H+ ions, so more ethanoic acid should be needed to produce H+ needed for the reaction, because it ionises to a lesser extent.
Isn't this supposed to a Unit 3 questin lol
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It's an acid-base reaction, not dissociation. The strength doesn't matter as far as i know.
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HNO3 and Ethanoic acid are both monoprotic and in equal concentrations. Former is strong and latter is weak. However, when titrating they would require the same NaOH as they would yield the same H ions till the equivalence point. When you are reacting NaOH with ethanoic acid you would be removing H ions from the system causing it to shift to the right until no H ions remain. This would be the equivalent to when no H ions remain for the HN03 and NaOH titration.
A bit muddled soz.
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Isn't this supposed to a Unit 3 questin lol
I think it's assumed knowledge from Unit 1 and 2 rather than Unit 4.