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GCSE chemistry question about carboxylic acids

I will put an image along with my question below
Reply 1
82D27E34-B8E9-4F8D-BF12-1D4D68738D6A.jpeg
Where did the 2 hydrogen atoms go??
When alcohols are oxidised, they form a carboxylic acid and water
(edited 1 year ago)
Reply 3
Original post by bears15
When alcohols are oxidised, they form a carboxylic acid and water

Thank you :smile:
Since your Figure 3 image seems like it'll probably be a bit misleading

Alcohols are oxidised by Oxidising agents (not just Oxygen) to form the respective carboxylic acid + water.

I did AQA Chemistry for GCSE, but if you do a different board, maybe you cover aldehydes/ketones (which alcohols are oxidised to first before Carboxylic acids, ketones don't get further oxidised)? If so, I can add more information.

The Oxidising Agent is commonly acidified potassium dichromate. Acidified means there's just some acid added, e.g. mild hydrochloric acid. Potassium Dichromate is K2 Cr2 O7 (spaces added for easier readability).

I don't know if you need to know a specific oxidising agent at GCSE (we were taught it, but we usually got taught extra information at my secondary school), but oxidising agents are usually just notated with a [O] in equations to make balancing easier as well.
Reply 5
Original post by Ira Acedia
Since your Figure 3 image seems like it'll probably be a bit misleading

Alcohols are oxidised by Oxidising agents (not just Oxygen) to form the respective carboxylic acid + water.

I did AQA Chemistry for GCSE, but if you do a different board, maybe you cover aldehydes/ketones (which alcohols are oxidised to first before Carboxylic acids, ketones don't get further oxidised)? If so, I can add more information.

The Oxidising Agent is commonly acidified potassium dichromate. Acidified means there's just some acid added, e.g. mild hydrochloric acid. Potassium Dichromate is K2 Cr2 O7 (spaces added for easier readability).

I don't know if you need to know a specific oxidising agent at GCSE (we were taught it, but we usually got taught extra information at my secondary school), but oxidising agents are usually just notated with a [O] in equations to make balancing easier as well.

I do AQA yes, we aren’t taught aldehydes and ketones. However that knowledge was useful since I’m gonna do A level chemistry, so i really appreciate the extra information. I’m now gonna research more about what you just told me once GCSEs are over (because you were taught about it in secondary school so surely it would be useful to know), thank you
(edited 1 year ago)
Original post by Idc123
I do AQA yes, we aren’t taught aldehydes and ketones. However that knowledge was useful since I’m gonna do A level chemistry, so i really appreciate the extra information. I’m now gonna research more about what you just told me once GCSEs are over (because you were taught about it in secondary school so surely it would be useful to know), thank you

My secondary school often teaches extra A-level content at GCSE for common subjects to be taken at A-level, so I don't know if it'll be useful for GCSE.

For reference, Maths is the most common A-level amongst people in my year (currently coming towards the end of Year 12), and Chemistry is a second, 93 out of some 150-ish people taking it. (Maths is 117)

At A-level though, for AQA, you are taught about aldehydes and ketones, and you do need to know the mechanisms and reagents/conditions for a number of reactions, including alcohol oxidation (for reagents), where knowing about potassium dichromate is useful. I have seen it come up in A-level mark schemes and the like as well, when testing for Organic Compounds.

(When Potassium dichromate is used to oxidise ANYTHING, be it an alcohol or sulfur dioxide, the change in ion oxidation states (an arbitrarily assigned value -- you'll learn about this at A-level) means that there is a colour change (starts orange, changes to green)).

This is not needed at all for GCSE, no need to look into it really. It could be useful to learn Organic Chemistry if you intend to do the Chemistry Olympiad in Year 12 (we were told about the opportunity to do this 2 weeks before the Olympiad and started being taught Organic chemistry many months later), but this is nothing to really worry about doing in your free time.

EDIT: The Chromium in the Cr2O7(2-) ion goes to Cr3+, which is why the colour change is consistent regardless of what you oxidise (since it's the chromium changing colour, not the thing you oxidise).
(edited 1 year ago)
Reply 7
Your secondary school sounds like a very good school. Do you mind saying the name of it? (You don’t need to reply due to privacy reasons btw)

I didn’t know there was a Chemistry Olympiad! You just made me want to research more. There must then also be a physics, maths and further maths Olympiad?
Original post by Idc123
Your secondary school sounds like a very good school. Do you mind saying the name of it? (You don’t need to reply due to privacy reasons btw)

I didn’t know there was a Chemistry Olympiad! You just made me want to research more. There must then also be a physics, maths and further maths Olympiad?

I'm not too comfortable stating my school, but it is a well known Grammar School, so yea, it is pretty good academically.

I confess I have no clue if there is a Further Mathematics Olympiad.

I do know that there is a Chemistry Olympiad (which includes Year 13 content, you can sit it any time I think, even in Year 9). This was early February this year. There's also the Cambridge Chemistry Challenge for Lower Sixth (year 12s), called C3L6, which this year will be happening mid-late June I believe. There is also a Physics Olympiad, many of them, as well as a Senior Physics Challenge for Year 12s (we also did an Intermediate Physics Challenge in Year 11). The Physics Challenge was about March time this year. There is also a Biology Olympiad, which happened about March time this year as well.

The Mathematical Olympiad also exists, these are ran by the UKMT. If you reach the cut-off score in the UKMT Maths Challenge, you can do the Kangaroo, and a higher cut-off score allows access to the Olympiad for free. Alternatively, you can pay for the Olympiad, but generally speaking, if you can't make the cut-off score, you might not do so well in the actual Olympiad.

Below are the respective websites:
https://edu.rsc.org/enrichment/uk-chemistry-olympiad
https://www.bpho.org.uk/past-papers/as-challenge
https://ukbiologycompetitions.org/british-biology-olympiad/
https://www.ukmt.org.uk/

For Maths and Chemistry, I know for definite that if you do extremely well then you can go on to represent the country in an international olympiad. I assume this is also the case for Physics and Biology.
Reply 9
I really appreciate the time you’ve spent responding to all my questions with so much depth, out of your free time, despite you probably being busy. Really really thank you, and I’m gonna look into the links now :grouphugs:

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