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Acid base question

ImageUploadedByStudent Room1460594628.448345.jpg

The mark scheme ticks the first box but I was just wondering because sulfuric acid and sodium hydroxide are both very strong should the ph balance to around 7? I don't see why the ph would fall between 8.3-10?


Posted from TSR Mobile
Original post by Lilly1234567890
ImageUploadedByStudent Room1460594628.448345.jpg

The mark scheme ticks the first box but I was just wondering because sulfuric acid and sodium hydroxide are both very strong should the ph balance to around 7? I don't see why the ph would fall between 8.3-10?


Posted from TSR Mobile


What you say is true, however for a titration to be successful the inflection (sudden change in pH) must pass through the pKa of the indicator.

In this case 1 drop of either acid or base around about the neutralisation point (equivalence) will take the pH from 4 to 10, or vice versa.

Hence phenolphthalein can be used for strong acid-strong base titrations.
Original post by charco
What you say is true, however for a titration to be successful the inflection (sudden change in pH) must pass through the pKa of the indicator.

In this case 1 drop of either acid or base around about the neutralisation point (equivalence) will take the pH from 4 to 10, or vice versa.

Hence phenolphthalein can be used for strong acid-strong base titrations.


So for the phenolphthalein indicator and in a strong acid strong base titration- the ph will always be greater than 7?


Posted from TSR Mobile
Original post by Lilly1234567890
So for the phenolphthalein indicator and in a strong acid strong base titration- the ph will always be greater than 7?


Posted from TSR Mobile


No, you have not read my post carefully enough ...

check out this interactive guide to indicators
Original post by charco
No, you have not read my post carefully enough ...

check out this interactive guide to indicators


thanks

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