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  1. C

    Help

    Have you finished the syllabus yet? It is near the end of the year 12 Advanced course.
  2. C

    Help

    @Hivaclibtibcharkwa, note that @jimmysmith560 formulae and mine are equivalent. The values that he has given for \sum x_i y_i = 304 \quad \quad \text{and} \quad \quad \sum {x_i}^2 = 252 \quad \quad \text{and} \quad \quad N = 8 match mine exactly, and the other two are equivalent as...
  3. C

    Help

    As far as I am aware, there are three options here: Option 1: Skip the question and score no marks. Option 2: Learn how to get the calculator to give you the equation. Option 3: Learn how to do the problem manually. Here is option 3: \begin{tabular}{ccccc}\text{Child}&\text{Exercise hours...
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    Mod 7 Oxidation of Alcohols

    Adding to what Jazz has said... One reason that redox reactions can be confusing is that it is not obvious that electrons are being lost or gained. This is one advantage of looking at half-equations that make this clearer. Also, the gain or loss of electrons can occur by transferring atoms...
  5. C

    is Covid 19/ pandemics environmental ethics or bioethics?

    Bioethics also brings in the issues around herd immunity - getting vaccinated not only to reduce one's own risk but the risk to others from transmission and to protect those who are unable to vaccinated for some reason. Ethics around COVID can also touch on issues of competing rights. The...
  6. C

    Dissolution of salts

    I would probably say something like: Since water is neutral on its own, dissolution of an ionic solid (like the salts in solutions X, Y, and Z) will only alter the pH from neutral (pH = 7 at 25 oC) if one or more of the resulting dissociated ions hydrolyses (reacts with water) to produce...
  7. C

    IR Spectra

    Good question. In my opinion, it is reasonable to expect an HSC student to get from the formula C3H6O to the compound being either propanone or propanal. The characteristic carbonyl stretch around 1700 cm-1 makes anything other than those two options unreasonable. The lack of any IR band that...
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    Help with linear equations homework

    @AmalJ, I realised that the b comes from the gradient-intercept form. The ability to see alternative approaches is something that stronger students often have. The best can also find wats to express their working in a way that is clear and persuasive. When I first read your answer, I had...
  9. C

    Dissolution of salts

    Ammonium nitrate will have an acidic solution as hydrolysis of its cation will result in the formation of hydronium ions. Sodium acetate will have a basic solution as hydrolysis of its anion will result in the formation of hydroxide ions. Sodium chloride will have a neutral solution as neither...
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    Help with linear equations homework

    Looking at the method you used, the part I don't like is that the pronumeral b just suddenly appears. However, the reasoning is sound. I would tweak your approach as follows: \begin{align*} \text{Any line parallel to } y &= 5 - \cfrac{x}{2}\ \text{must have the same gradient} \\ \text{and so...
  11. C

    The answer is B. But don’t ectoterms bask in the sun to raise their temperature?

    PS: This is a mix of knowledge of science education and general understanding of ectotherms basking to enable activity and of concepts like genetics (which is both chemical and biological) and evolution. I will readily defer to those more knowledgeable on specific issues of biology, though I...
  12. C

    Glucose is 100% absorbed in the nephrons. So how is the answe not C?

    Most definitely not. I have the qualifications and experience to claim expertise in chemistry and in high school / some uni levels of maths. I have never studied biology formally, but I have studied science education and many biological situations from a chemical perspective. I also have a...
  13. C

    Glucose is 100% absorbed in the nephrons. So how is the answe not C?

    Bear in mind that excessive glucose levels (in uncontrolled diabetes, for example), leads the kidneys to eliminate glucose in urine, so glucose can be disposed of via the kidneys as well as being retained.
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    The answer is B. But don’t ectoterms bask in the sun to raise their temperature?

    I agree with Eagle Mum on (A) as the only thing that we absorb from the sun is energy in the form of light, and light of different wavelengths carries different amounts of energy. The biosynthesis of vitamin D3 for animals is a two-step process whereby UV-B light of wavelengths 295 to 300 nm...
  15. C

    Saw the solution but they had a drawn a huge table. Is there another way of solving this?

    Strike that request... it's the 2018 HSC. :oops::embarassment:
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    Saw the solution but they had a drawn a huge table. Is there another way of solving this?

    My setting out would be a little different but I do think the table is a very helpful tool for solving the question. @Hivaclibtibcharkwa, what specific source is this from NESA? I don't recognise it. Thanks
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    Lockdown extension

    Bear in mind with trials that there are many schools who aren't able to decide for themselves as they have bought trial papers and will be stuck with whatever changes in the embargoes are made by the copyright holders. All schools using CSSA will move together, for example..
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    Saw the solution but they had a drawn a huge table. Is there another way of solving this?

    were the answers 4/9 and 5/27? Where is this from?
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    A general question for limits

    I can similarly rewrite \cfrac{\sqrt{x^2 + x^3}}{x} = \cfrac{\sqrt{x^2(1 + x)}}{x} = \cfrac{\sqrt{(-1)^2 x^2(1 + x)}}{x} = \cfrac{\sqrt{(-x)^2(1 + x)}}{x} = \cfrac{-x\sqrt{1 + x}}{x} and so get the limit as -1 after cancelling and substituting x = 0. As Trebla notes, \cfrac{\sqrt{x^2 +...
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    Chemistry with standard math

    There is no maths in chemistry that is beyond standard maths level. In my opinion, the difficulty that students have with the maths in chemistry has far more to do with it being explained in an overly complicated way than it has to do with the difficulty of the maths itself. This is not to say...
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