HSC Chemistry Exam Solutions / Thoughts (6 Viewers)

[Idkwhattoput]

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

Yeah. Surprising it hasn't been leaked early yet

 

[Arrowshaft]

But identifying the reagents didny mean the

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

Reagents and reactants are mostly used interchangeably, however, reactants more specifically are used up in the reaction

 

[Idkwhattoput]

Reagents and reactants are mostly used interchangeably, however, reactants more specifically are used up in the reaction

You or someone else previously mentioned that they 'forgot' to talk about how esterification produces water when it was mentioned that reagents need to be stated. So, do we actually need to state what was produced as a byproduct?

 

[Arrowshaft]

You or someone else previously mentioned that they 'forgot' to talk about how esterification produces water when it was mentioned that reagents need to be stated. So, do we actually need to state what was produced as a byproduct?

That wasn’t me, I almost forgot. But yeah, I’d assume you’d have to mention by products since it asks to describe the process

 

[Idkwhattoput]

That wasn’t me, I almost forgot. But yeah, I’d assume you’d have to mention by products since it asks to describe the process

Fair enough. I thought they were implying you're supposed to because it says to mention the reagents.

 

[Arrowshaft]

Fair enough. I thought they were implying you're supposed to because it says to mention the reagents.

Well reagents mean reactants, the by products are useless so they aren’t really used in the next step as reactants

 

[Jendeukie]

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

i don't have answers so i can't check for strong acids and bases basically it was one of the last four right? i was desperate so when i was up, signed and walking out (please don't begrudge me lmao i was literally leaving) i just chucked a glance at the smart girl's sheet before me - only had time to look at the last four questions - and i mean all were same but last so fingers crossed. i got a lot of Ds lmao idk

i also lost radioactive and last one! radioactive was just WTF man i have no idea


also honestly very surprised that no answers for MCQ or paper has been leaked yet. didn't matrix release full bio exam answers? see ugh idk if i wanna go over short answe bec I'm a full wimp, i just want the first part

 

[worldno17]

i don't have answers so i can't check for strong acids and bases basically it was one of the last four right?

the strong acid/base one was q18, think i got A...? not sure though, literally can't remember the equation

 

[worldno17]

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???

sorry haha i was the reactant/reagent person. was probably a little cooked last night - i think it's allg, u only needed to talk about reactants. and yes, that is correct - it was in my notes so i'm assuming i got it from either tutoring or one of my textbooks. you need the acid bc otherwise substitution w water is too slow.

 

[Jendeukie]

the strong acid/base one was q18, think i got A...? not sure though, literally can't remember the equation

I got D strongest acid HF and strongest base CH3COO-

it's okay, now when i think about it i answered part 1 of that AAS question really badly. all i said was they form precipitates, i didn't even talk about how one metal has a higher ksp than the other etc. etc.

yep, i'll defs need to stop thinking now. it's just that i don't have any exams left so i kinda have nothing to do but think about it HAHA this is harder than i thought it would b

 

[dotwingz]

I got D strongest acid HF and strongest base CH3COO-

it's okay, now when i think about it i answered part 1 of that AAS question really badly. all i said was they form precipitates, i didn't even talk about how one metal has a higher ksp than the other etc. etc.

yep, i'll defs need to stop thinking now. it's just that i don't have any exams left so i kinda have nothing to do but think about it HAHA this is harder than i thought it would b

The strongest acid was CF3COOH, and the strongest base was F-.

Tbf i only knew that because after a 10h binge of Breaking Bad i decided to look up about hydroflouric acid, and saw that it was weak but corrosive,

IIRC i looked it up after the exam and CF3COOH has a pKa of like -0.25, so it is very strong, hence its conjugate base is weak.

 

[Jendeukie]

The strongest acid was CF3COOH, and the strongest base was F-.

Tbf i only knew that because after a 10h binge of Breaking Bad i decided to look up about hydroflouric acid, and saw that it was weak but corrosive,

IIRC i looked it up after the exam and CF3COOH has a pKa of like -0.25, so it is very strong, hence its conjugate base is weak.

omg wait i think it's because i mistook CF3COOH for acetic acid? OMG AKSKSKS THAT'S SO SAD I'M SO BLIND WTF

ive officially done better in eco multiple choice i didn't know this was possible

 

[lalajellyjoy]

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???

wait so do we need to write what the compounds were because i didn't do that i just assumed that reagents meant what was needed for the reaction like sulfuric acid, heat, etc. but for cholorethane to ethanol, you needed NaOH and heat im pretty sure? some say reflux not heat tho

 

[Jendeukie]

can someone please explain why it was possible for the equilibrium constant to be 3 if the other acid was stronger? it lied to the right, i.e. concentration of products greater, and i thought that meant HF ionised to a greater degree than the other way around, because the other acid was on the right and if it were relatively stronger i don't understand why there wouldn't be a lot more CF3COO- or whatever in the solution so the equilibrium constant would've indicated a reaction lying to the left
not to mention if HF were a weaker acid, more of it would be in its molecular form and that would mean even more molecules on the left

EDIT: aksksksk yeah it's acetic acid CH3COOH hence i was right SORRY FR GETTING UP IN ARMS

 

[worldno17]

can someone please explain why it was possible for the equilibrium constant to be 3 if the other acid was stronger? it lied to the right, i.e. concentration of products greater, and i thought that meant HF ionised to a greater degree than the other way around, because the other acid was on the right and if it were relatively stronger i don't understand why there wouldn't be a lot more CF3COO- or whatever in the solution so the equilibrium constant would've indicated a reaction lying to the left
not to mention if HF were a weaker acid, more of it would be in its molecular form and that would mean even more molecules on the left

EDIT: aksksksk yeah it's acetic acid CH3COOH hence i was right SORRY FR GETTING UP IN ARMS

huh what? is this question 18? where's the acetic acid coming from lol
also wasn't the equilibrium constant way smaller than 1? i also don't remember the reaction equation...smh, where is the paper?!

i think i got the same thing as dotwingz tho
edit: yeah, i just searched up their respective pka values, cf3cooh is stronger than hf

The strongest acid was CF3COOH, and the strongest base was F-.

do you remember which option this was? sounds like A - but i'm not 100% certain.

 

[dotwingz]

do you remember which option this was? sounds like A - but i'm not 100% certain.

I forgot, but my friend put down A and had the same answer. So i would say its A.

 

[Jendeukie]

huh what? is this question 18? where's the acetic acid coming from lol
also wasn't the equilibrium constant way smaller than 1? i also don't remember the reaction equation...smh, where is the paper?!

i think i got the same thing as dotwingz tho
edit: yeah, i just searched up their respective pka values, cf3cooh is stronger than hf


do you remember which option this was? sounds like A - but i'm not 100% certain.

I think we just need the paper. I’m totally blind (I do remember a higher than 1 constant tho) and I asked two of my friends and they got the same thing, so I thought it was acetic. You guys know your stuff though and both of you got something else, so we could’ve just all misread the question at my school HAHA

 

[worldno17]

I think we just need the paper. I’m totally blind (I do remember a higher than 1 constant tho) and I asked two of my friends and they got the same thing, so I thought it was acetic. You guys know your stuff though and both of you got something else, so we could’ve just all misread the question at my school HAHA

oh nah i don't think it was acetic, the acids in the reaction were hf and cf3cooh. i just can't remember which one was ionising on the LHS or the value of Keq so can't figure out the full answer rn.
i'm just procrastinating on phys hahaha (since it hasn't counted for me in my past atar estimates ;-; i'm still trying though!!!)

 

[Jendeukie]

oh nah it's defs not acetic, the acids in the reaction were hf and cf3cooh. i just can't remember which one was ionising on the LHS or the value of Keq so can't figure out the full answer rn.
i'm just procrastinating on phys hahaha (since it hasn't counted for me in my past atar estimates ;-; i'm still trying though!!!)

Me expecting my IPT from two years ago to count in HAHA

This just means both me and all my friends misread OMG embarrassment! I concede defeat. I do remember the equation tho - equilibrium with HF on the right, other acid on left. Idk why I remember the constant was 3, maybe that’s just placebo too? I based my entire answer off it being bigger than 1, but at this point I’m going to consider it a warped memory.

 

[worldno17]

Me expecting my IPT from two years ago to count in HAHA

This just means both me and all my friends misread OMG embarrassment! I concede defeat. I do remember the equation tho - equilibrium with HF on the right, other acid on left. Idk why I remember the constant was 3, maybe that’s just placebo too? I based my entire answer off it being bigger than 1, but at this point I’m going to consider it a warped memory.

now ur seriously making me doubt my memory HAHA, can the paper pls be released ;-; nesa will probs release it next mon.