HSC Chemistry Exam Solutions / Thoughts (1 Viewer)

[Arrowshaft]

I just did NaOH + heat for substitution of the chloroethane; thats how Ive learnt it.

Well you dont really need heat for NaOH, heat is usually for water but i may have been taught wrong

 

[flowerp]

For the last q. I also said that via a substitution reaction with NaOH we can get ethanol, but I also forgot to include the conditions ugghhhh! Hope we don't lose marks!!! I've already lost 10 marks for sure ... and really want a b6 uugghhh the sheer amount of silly mistakes I make in EVERY EXAM is ridiculous!

 

[CarbonMini]

For the last q. I also said that via a substitution reaction with NaOH we can get ethanol, but I also forgot to include the conditions ugghhhh! Hope we don't lose marks!!! I've already lost 10 marks for sure ... and really want a b6 uugghhh the sheer amount of silly mistakes I make in EVERY EXAM is ridiculous!

I mean as @Arrowshaft has mentioned above u only apparently need NaOH with no other conditions? IDK, im pretty sure you need heat, Ill check my textbook in the morning

 

[flowerp]

So I just googled, apparently primary haloalkanes require a catalyst with NaOH due to the slow reaction which occurs, and reflux conditions can be used

 

[CarbonMini]

So I just googled, apparently primary haloalkanes require a catalyst with NaOH due to the slow reaction which occurs, and reflux conditions can be used

Oh shoot I mean its a 7 marker so hopefully what u wrote was enough??? Im starting to get worried because I only wrote heat, not reflux...

 

[flowerp]

This website says reflux: https://www.chemguide.co.uk/mechanisms/nucsub/hydroxide.html - Hopefully we will both get the marks either way!

 

[Arrowshaft]

I’m sure it’ll be fine, max we could lose is 1 mark anyway. also if our other info is coherent enough it should be fine and we might mot lose a mark

 

[Jendeukie]

so lol...
that difluoro question in the multiple choice? how many carbons in the molecule? anyone sure of their answer for that? only 2 numbers i remember are 750 and 1500

 

[Arrowshaft]

so lol...
that difluoro question in the multiple choice? how many carbons in the molecule? anyone sure of their answer from that? only 2 numbers i remember are 750 and 1500

1500? cant rrally rmber

 

[CarbonMini]

so lol...
that difluoro question in the multiple choice? how many carbons in the molecule? anyone sure of their answer from that? only 2 numbers i remember are 750 and 1500

Im pretty sure its 1500. Everyone that I know got 1500.

 

[Arrowshaft]

Yeah think it was. I just remember i multiplied some number by 2, i think i got 1500

 

[Jendeukie]

1500? cant rrally rmber

OKAY haha i got that too
can't remember all the other MC i felt were sucky so guess i'll have to live in suspense until december 16th

last thing - i remember in the very first q they were asking for a test to differentiate between the aldehyde and the ketone lol... vaguely remembered tollens' reagent and how aldehyde reduces silver ions to silver, but ultimately had no idea what the actual reaction equation was. hope they don't penalise me.

 

[Arrowshaft]

OKAY haha i got that too
can't remember all the other MC i felt were sucky so guess i'll have to live in suspense until december 16th

last thing - i remember in the very first q they were asking for a test to differentiate between the aldehyde and the ketone lol... vaguely remembered tollens' reagent and how aldehyde reduces silver ions to silver, but ultimately had no idea what the actual reaction equation was. hope they don't penalise me.

either oxidation with potassium dichromate, aldehyde shiuld change colour from orange to green when oxidised to an acid. After to confirm solid na2co3 can be dissolved producing bubble and u know the rest

 

[Jendeukie]

either oxidation with potassium dichromate, aldehyde shiuld change colour from orange to green when oxidised to an acid. After to confirm solid na2co3 can be dissolved producing bubble and u know the rest

omg i can't believe it yes that's such an obvious thing! i'm so dumb hahaha i got caught up in the silver mirror whatever. like, aldehyde reduces the ions to silver and ketone remains unreactive. now that i think about it, i wouldn't be writing equations for that either so hope they don't penalise

thanks bro and gl on your future exams!

 

[Arrowshaft]

omg i can't believe it yes that's such an obvious thing! i'm so dumb hahaha i got caught up in the silver mirror whatever. like, aldehyde reduces the ions to silver and ketone remains unreactive. now that i think about it, i wouldn't be writing equations for that either so hope they don't penalise

thanks bro and gl on your future exams!

Thanks, you too (if you have any )

 

[CarbonMini]

OKAY haha i got that too
can't remember all the other MC i felt were sucky so guess i'll have to live in suspense until december 16th

last thing - i remember in the very first q they were asking for a test to differentiate between the aldehyde and the ketone lol... vaguely remembered tollens' reagent and how aldehyde reduces silver ions to silver, but ultimately had no idea what the actual reaction equation was. hope they don't penalise me.

I lost like 3 marks in MC - the strong acid strong base, radioactive one and q20...
Though I did well in short answer so yeah... Honestly found MC to be the hardest part of the test

 

[lalajellyjoy]

Na probably 4 marks for naming all the compounds and 3 for justifying each step and its reagents and conditions

I didn't know we had to nameeee them Wthhhhh arghhh

 

[lalajellyjoy]

I remember specifically adjusting my answer to clearly outline each compound as it said something like 'identify the reagents in each reaction'.

But identifying the reagents didny mean the

I remember specifically adjusting my answer to clearly outline each compound as it said something like 'identify the reagents in each reaction'.

I thought identifying reagents was what was needed for the reaction to occur?? Is that not right?

 

[1-99]

Hey guys, does anyone seem to have the Chem paper? I can't find it anywhere!

 

[Idkwhattoput]

But identifying the reagents didny mean the

I thought identifying reagents was what was needed for the reaction to occur?? Is that not right?

I'm as surprised as you. I always thought reagents was synonymous with reactants. Also, for that last question (chloroethane to ethanol), is water and sulfuric acid catalyst correct?? I wrote that but I assumed it was wrong because I can't seem to find them anywhere???