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re: HSC Chemistry Marathon Archive You got it, well done :)

re: HSC Chemistry Marathon Archive A student wished to determine the percentage of calcium carbonate in a shell found at the beach. The clean dry shell, which weighed 1.306g, was placed in a small beaker and 10mL of 5mol/L of hydrochloric acid was added. When the shell had completely dissolved...

re: HSC Chemistry Marathon Archive HCO3- + H2O --> H2CO3 + OH- Is this the equation?

I thought LDPE required high pressure and temperature, while HDPE requires much lower pressure and temperature. This is what I've learnt: 1 and 2: no. For LDPE, the initiator activates the process by opening up the double bond of an ethylene molecule. For HDPE, the catalyst does this and...

re: HSC Chemistry Marathon Archive HCO3- is amphiprotic though, so it can act as either a base or an acid by either accepting or donating a proton. Acting as an acid: HCO3- + OH- --> CO32- + H2O Acting as a base: HCO3- + H3O+ --> H2CO3 + H2O Don't really understand what you're...

The initial pH is actually 1, not 3.3 The concentration of HCl is 0.1M (i.e. 0.1mol/L). 0.005x0.01 = 0.0005 gives you the moles of HCl.

re: HSC Chemistry Marathon Archive Good try, but this is incorrect. When calculating pH, you have to take into account the amounts of H+ and OH- present, not the actual acids and bases themselves. The answer's here: n(KOH) = 0.0075mol n(OH-) = 0.0075mol (since KOH is a strong...

re: HSC Chemistry Marathon Archive Yeah, sorry lol at 100 kPa and 25oC 1 mol ---- 24.79L x mol ---- 15.0L x = 0.6050...moles n = m/M M = m/n = 1.22g/0.6050...moles = 2.016253..g/mol Since all the gases occur as diatomic molecules, divide the molar mass by 2...

re: HSC Chemistry Marathon Archive Hydrogen gas.

re: HSC Chemistry Marathon Archive Calculate the pH of the resulting solution when 50.0mL of 0.15mol/L potassium hydroxide solution and 150mL of 0.10mol/L sulfuric acid are mixed.

re: HSC Chemistry Marathon Archive Nah, it's C. 2006 HSC, q9.

re: HSC Chemistry Marathon Archive Yep, it is! Which stateent best describes the equivalence point in a titration between a strong acid and a strong base? (A) The point at which the first sign of a colour change occurs (B) The point at which equal moles of acid and base have been added...

re: HSC Chemistry Marathon Archive lol woops. fixed it.

re: HSC Chemistry Marathon Archive How many isomers can exist for C3H6Cl2?

Firstly, why do you want to drop maths, because you don't like or aren't doing well? If you're not doing well because you're not studying, maybe you could start studying and see how you go. If you do decide (and you're allowed) to pick up bio, you don't need prelim for hsc. And catching up on...

Yeah, this is right. THe oxidation state of chromium goes from 6+ --> 3+ So, it has gained 3 electrons and the oxidation state has decreased.

everything you just said sums up exactly how i feel right now but, don't dwell on it, focus on your other subjects now (:

this

(:

sqrt(450) simplified to 15sqrt(2)