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  1. wizzkids

    Why are chlorine and bromine ions acidic?

    Thanks for the [!!!]WARNING[!!!]. Better stop swimming in the ocean - too much chloride
  2. wizzkids

    Mod 6 Q

    Ignore all the conversation about commutators and radial magnetic fields. Just consider a single current loop in a uniform B-field as shown below: The vertical segments are experiencing a constant force shown by the red vectors, and the two forces constitute a couple or moment. The horizontal...
  3. wizzkids

    Trial Q

    The mass loses kinetic energy and gains GPE as it moves from A to B. Let the velocity at the bottom be v1 and the velocity at the top be v2 The change of gpe is U = 2mgr. The change of KE is U = -1/2 m (v12 - v22) Equate the two expressions and eliminate the common factor "m" you get: 2gr =...
  4. wizzkids

    help

    The mass of solution is M= 14 g + 100 g = 114 g The density rho ρ of the solution is ρ= 1.060 g/mL so divide M by ρ and you get V=107 mL of solution. The 14 grams of the hydrous MgSO4.7H2O contains n = 0.0568 moles. Therefore divide n by V and you get 0.53 mol/L
  5. wizzkids

    chem question

    Ava-Gardner
  6. wizzkids

    Ca(OH)2

    You are using the Arrhenius theory of a strong base. The Brönsted-Lowry theory is not restricted to aqueous solutions. If Ca(OH)2 is a good proton acceptor (which it is), then it is a strong base according to the latter theory.
  7. wizzkids

    mod 7 organic states of matter

    I think any further debate will likely result in arcane hair-splitting. However, for students sitting their HSC Chemistry exam, there will be just three states of matter, they are solid, liquid and gas and the only other mixture they are likely to be examined on is the aqueous mixture, and we...
  8. wizzkids

    mod 7 organic states of matter

    Thanks for that contribution, you got me thinking that can't be right because IUPAC has reserved the term "sol" for colloidal suspensions, so I went to the references. In the Journal of Pure Appl. Chem., Vol. 80, No. 2, pp. 233–276, 2008. doi:10.1351/pac200880020233 © 2008 IUPAC they give the...
  9. wizzkids

    NSG 2020 Q31 - no calculation for answers PLEASE HELP

    Obviously this student was in a bit of a hurry and missed the equivalence point by a substantial margin. :( If you add the last drops of NaOH slowly you should be able to achieve a precision of 0.1 mL in the aliquot. Look at the results at 20.0 mL and 24.0 mL. This is where the inflection...
  10. wizzkids

    mod 7 organic states of matter

    Ahh, no. We call them liquids because that is their standard state at 25oC. If the ester coincidentally happens to be dissolved in a reaction mixture like an alcohol, then you still call it a liquid. The adjective "aqueous" (aq) should be reserved for substances that are dissolved in water, or...
  11. wizzkids

    Physics 2019 Sydney BOys

    Yes, it should be tan θ. I disagree with that equation given in the sample answer. The result is correct, but the equation is wrong. Here is the free body diagram of the car. The car is subjected to just two forces, they are W the force of gravity and FN the normal force from the road. The net...
  12. wizzkids

    mod 7 organic states of matter

    Most esters are liquids at room temperature.
  13. wizzkids

    mod 7 organic states of matter

    You state that gases are (g) and liquids are (l). Students are not required to memorise the physical states of organic compounds for the HSC Chemistry exam. You should be able to work these facts out from the context of the question. If a question requires you to write a chemical equation...
  14. wizzkids

    polarisation

    No you're not. You're doing just fine. Just make sure you read all parts of the question, and underline the important facts.
  15. wizzkids

    polarisation

    In the original post, it says Io is the intensity after leaving polarising filter #1. Therefore Malus' Law only applies to the interaction between polarizing filter #2 and filter #3. Therefore the intensity after leaving filter #3 varies from zero to 0.5 Io.
  16. wizzkids

    polarisation

    This is a common misconception, but the influence of the first polarizing filter over the third polarizing filter (or the second analyser if you want to refer to it that) is irrelevant once you introduce the middle polarising filter. I have done this experiment many times in class with three...
  17. wizzkids

    polarisation

    Yes, the intensity of the light will halve after passing through the first filter, but it will not halve after passing through the second filter. The law about halving the intensity only applies to unpolarised light that has passed through an ideal polarising filter. Once the light has become...
  18. wizzkids

    mass spec isotopes

    Regarding H, C and O. Look at those values for abundance. There is only one dominant isotope, the other isotope is totally insignificant for the mass spectrum, so no need to memorise those ones. Regarding those other elements, as part of your general knowledge in Chemistry, you should be aware...
  19. wizzkids

    QATS Trial 2019

    First, we must assume that the wave fronts are drawn as if they are synchronous, that is they are generated at the same times. Next we look for places where the first wavefront from the left-hand source intersects with the third wavefront from the right-hand source, and draw a point. This is a...
  20. wizzkids

    NH3

    H2O donates a proton to NH3. The Bronsted-Lowry model of a base is any substance that is a proton acceptor.
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