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Hard Moles Questions Watch

1. Please could someone link me some hard moles equations suitable for an AS Chemistry student. I would appreciate hard moles questions that really make me apply my knowledge.

Thanks a lot!!!!
2. A sample of solid ethanedioic acid () has been contaminated with potassium ethanedioate (). A 1.780 g sample of this mixture was made up to a 250 cm3 solution with distilled water. A 25 cm3 sample was titrated against 0.100 mol dm-3 sodium hydroxide, requiring 17.35 cm3. Another 25 cm3 sample was acidified with sulphuric acid and titrated against 0.0200 mol dm-3 solution, requiring 24.85 cm3. Calculate .
+ .

You will have to think very carefully about redox reactions and acid-base reactions to answer this question.
3. (Original post by B_9710)
A sample of solid ethanedioic acid () has been contaminated with potassium ethanedioate (). A 1.780 g sample of this mixture was made up to a 250 cm3 solution with distilled water. A 25 cm3 sample was titrated against 0.100 mol dm-3 sodium hydroxide, requiring 17.35 cm3. Another 25 cm3 sample was acidified with sulphuric acid and titrated against 0.0200 mol dm-3 solution, requiring 24.85 cm3. Calculate .
+ .

You will have to think very carefully about redox reactions and acid-base reactions to answer this question.
Thanks for the question, this is really tough too I have calculated the moles of the titrations and I don't know what I should do next?
4. Think about the reactions and what it means.
The base (NaOH) added will only react with the acid (acid-base) reaction (advice is to write the equation for this) but the KMnO4 will react with the C2O4- ions in both the acid and the impurity (the K2C2O4.xH2O).
Perhaps you might want to post your workings?
5. (Original post by B_9710)
Think about the reactions and what it means.
The base (NaOH) added will only react with the acid (acid-base) reaction (advice is to write the equation for this) but the KMnO4 will react with the C2O4- ions in both the acid and the impurity (the K2C2O4.xH2O).
Perhaps you might want to post your workings?
I don't understand what the equation should be.
do you mean
K2C2O4.XH2O + KMnO4
and
H2C2O4.2H2O + NaOH
if so what would the products be?
6. (Original post by HiThere8964)
I don't understand what the equation should be.
do you mean
K2C2O4.XH2O + KMnO4
and
H2C2O4.2H2O + NaOH
if so what would the products be?
For the equations forget about the .H2O (called water of crystallisation I believe) as its not important for the reactions.
The acid-base reaction between NaOH and the acid H2C2O4 (forgetting the .H2O now) is
.
Use this to work out the moles of H2C2O4.2H2O in the 25cm3 sample.
Use the half equation given to write a redox equation between MnO4- and C2O4 2-.
Then see where you can take it from there.
7. (Original post by B_9710)
For the equations forget about the .H2O (called water of crystallisation I believe) as its not important for the reactions.
The acid-base reaction between NaOH and the acid H2C2O4 (forgetting the .H2O now) is
.
Use this to work out the moles of H2C2O4.2H2O in the 25cm3 sample.
Use the half equation given to write a redox equation between MnO4- and C2O4 2-.
Then see where you can take it from there.
Thanks a lot for the question and the help I will try and rep you again as soon as I can!!
8. I once punched a mole and I knocked it clean out.

Probably wasn't all that hard.
9. (Original post by HiThere8964)
Thanks a lot for the question and the help I will try and rep you again as soon as I can!!
No problem
10. I still cant get it can you post a worked solution please,

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