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A chemical bond is a bound state, which has negative potential energy. Essentially, when a bond is formed, you lose potential energy in the form of heat. An analogy would be you and the Earth (i.e. gravity). On the Earth's surface, you have no potential energy but if you were elevated (e.g. in...

I disagree with the comments here. There is an assumption that the emission lines are in the visible spectrum. It happens to be true for many metals (e.g. Na, Ca). However, for anions (particularly the common ones like chloride, bromide, sulfate), the emission lines might not be or the...

To completely cancel out, it needs to be the same elements but if they're different, then the net vector will be the sum of all the vectors.

Pretty sure the wire is getting pushed in the D direction.

With just ethanol and hexanoic acid? Definitely not. If you have some sulfuric acid in there, you'd probably see partial completion but these reactions are very slow at rt. The sieves will only help if you can exceed the activation barrier.

A systematic error should be predictable and consistent (e.g. an incorrectly calibrated balance that reads 2% higher than expected for all weights). Improper rinsing is not predictable, so it's wrong to say that it's a systematic error. This is much more consistent with a random error.

Yeah, I don't blame the teachers at all. It's a pain to become a teacher with X years of experience in industry or research. To be honest, I was taught in HS that you can improve reliability by repetition. In a sense, it's not completely wrong because if you repeat a method and get similar...

Everything you've said here is correct (from both an industrial and research perspective). I'm wondering whether this question is difficult for students to answer because validity and accuracy are not clearly defined at HSC-level beyond "is it a reasonable method?" and "how close is it?". In...

The funny thing is, I don't think most chemists care whether you call it soluble/insoluble/slightly soluble when you have the exact value, and quite frankly, I had no idea there was a cutoff to define whether something was soluble or not. It's definitely context-dependent because I've seen...

This is what I hate about borderline cases. I'd consider octanol to be "slightly soluble" but there's a problem if we're just going with soluble or insoluble.

The questions are also written in a way where if quickly form an answer without thinking, it's easy to get it wrong. There's also a bunch of questions where I'm like, lol, don't remember a single thing about this stuff (e.g. some of the solubility stuff).

...and it's not even a flow chart.

That's...bad. Really bad. I can imagine a lot of students giving completely valid answers and getting marked down for it.

Yeah, good luck to the marker. You'd have to assess every single answer and consider whether it's valid or not. I could see each answer taking 5+ minutes to evaluate properly. It would be...highly varied.

Yeah, that question is just poorly designed. I know a few people that got blisters from glacial acetic acid which appear instantly. In contrast, I've had 37% HCl on my skin but some running water and there are no issues. It's surprising how much more dangerous some weak acids can be. There's a...

Yeah, it'd be nice if the HSC actually taught a few different approaches to oxidation/reduction reactions in the HSC (e.g. LiAlH4, NaBH4) so they can actually ask questions that aren't just adding potassium permanganate. For the one in purple, this is an example of a question I don't like...

I agree with this but I understand that it's difficult to achieve without a big review panel with a broad knowledge base. There's a stupid amount of chemistry that I don't know much about (including some in this trial...either that, or I just forgot it lol) and even then, it's easy to know...

Yeah, in the industry (which I'm adjusting to), a single data point (at each concentration) is not sufficient for linearity. Instead, they expect precision data for several data points. For example, at a very low concentration, you'd run the 2 ppb test 6 times and do the same at the top and...

Yeah, something like that. I already got the question wrong because I can't read so. There's that lol. Happens to all of us xD Q14. Yeah, it's just that...what you see is very dependent on how the reaction is set up and the techniques aren't really used anymore. Overall though, the trial was...

Q11. Yeah, I didn't read the question properly (and also wasn't really thinking lol). A buffer doesn't require any specific concentration or ratio as long as both conjugates are present in decent quantities (I think the definition is deliberately left vague). Q14. This is why I'm not a fan of...