Originally posted by TheSpaceManatee:for the observation question in planning (2 marks) can i say effervescence and deep blue solid dissolves in excess h2so4 without saying a blue solution is formed?
For the K more reactive than copper question, I talked about much higher effective nuclear charge in Cu hence 4s1 electron more tightly bound to nucleus blah blah... correct?
for the draw nucleophillic addition mechanism, in the second step is it the lone pair on O just attack a H+ or is it lone pair attack H in H2O to give the product and OH-?
and for the NO2 effect on environment can just say photochemical smog and acid rain without talking about polluting river or corroding limestone buildings?
Also, for slow corrosion of coper i said that a layer of CuO forms that will slow down corrosion, is that correct?
other than that should be ok, but I skipped 10 marks of planning, is it still possible to get A? :( Thanks
Yes, but whether your answer scores all 4 marks depends on how complete your points are.
The O- must abstract a H+ from H2O. H+ alone not accepted because it's strongly alkaline pH.
Can.
Yes.
You calculate your overall % yourself lor. Right now A grade boundary should be approx 75%. Let's see P3 and P1.
Haha, quite worried for this paper, in terms of keywords and explanations. I think Paper 3 would be very integrated, with energetics, electrochem, I.E, Atomic structure, ksp all those...
I confuse about the average number of average C=C number is 2.97 or 2.85 and for NO2 whether the respiration problem?
I don't know how to answer the one which says no2 oxidised so2. anyone knows how? I can't seem to get from data booklet
Originally posted by qsx:I confuse about the average number of average C=C number is 2.97 or 2.85 and for NO2 whether the respiration problem?
Acceptable, if stated correctly.
Originally posted by qsx:I confuse about the average number of average C=C number is 2.97 or 2.85 and for NO2 whether the respiration problem?
Mine was 2.85. Not sure if its right.
Originally posted by captainkidzs:I don't know how to answer the one which says no2 oxidised so2. anyone knows how? I can't seem to get from data booklet
will you posting your answers?? Im abit paranoid, i dk if i was missing any pages lol the last question was about decreasing pH isit?
Ultima, so sadistic :(
Usually will the majority be in B or C based on the bell curve? I have always failed chem in school, hope to get at least a C :(
Originally posted by UltimaOnline:
Google it out now lor. Quite straightforward leh. Just write equations only, question never ask you to draw out curved arrow mechanisms (which would have been a lot more fun).
i see 2 results, no2 oxidise so2 to so42- and becomes n2, and no2 oxidise s02 to s03 and becomes no. Which one correct or both accepted?
Hi for the nucleophilic addition question i saw that it was alkaline so initially i wrote h20+h20 to produce h30+ and oh-(generation of catalyst ) on top of the reaction mechanism (my mechanism was correct)) but when the paper was collected i realised h20 cant produce h30+ and oh- simultaneously to make an alkaline solution but at that point in time i couldnt erase that part, will i lose any marks for writing a wrong statement?
And also for the qn which asked us to state the reaction mechanism with iodine and oleic acid, its supposed to be electrophilic addition but i wrote electrphilic addition. Do you think cambridge will accept my ans and award me the mark?
I would think they should accept only NO2+S02=SO3+NO then regeneration bla bla bla
so its like a homogeneous catalyst and Oxidising agent
i would think electrophilic is a very important mark unless your examiner was marking your script while asleep
what does reactivity of cu and k have to do with? most will relate to IE but is it possible to relate to metallic bonding? since metallic bonding in cu is higher than K so less likely to donate electrons for reaction
for the Cu and aqueous ammonia ionic eqn qn, do i just use the cu(h2O)6 2+ bla bla -> cu(nh3)4 2+?
For the Cu and ammonia question,
I believe you have to use the Cu + NH3 = [Cu (NH3)4]2+ Eqn and the alkaline reduction of O2 to form ur ionic eqn
Specifically, the Cu exists as a solid metal (s), and not an ion, so you should not have it become the cuh2o62+
The NxHy partial pressure is 1.4E10^-10, is it correct?
And the heterogeneous catalyst I need to mention about desorbed ,adsorbed, adsorption and surface concentration and weaken the bond. Is there some more need to be added?
Originally posted by Thefire521:For the Cu and ammonia question,
I believe you have to use the Cu + NH3 = [Cu (NH3)4]2+ Eqn and the alkaline reduction of O2 to form ur ionic eqn
Specifically, the Cu exists as a solid metal (s), and not an ion, so you should not have it become the cuh2o62+
Pardon me maybe a stupid question but the alkaline oxygen reduction equation I used was O2 + 2H2O + 4e- ---> 4OH- correct?
@qsx I also said lower activation energy of the reaction but not sure if required.
Will you be spotting the topics for H2 chemistry for paper 3? Thanks
Yes i think the partial pressure seems right but in 3sf.
Since the q was only 2 marks for explanation and only asking how it increases the rate of reaction (and not the whole mechanism), the answer should focus mostly on increasing concentration, higher number of effective collision, correct orientation and also straining critical bonds so lower activation energy.
Yeah thats the right O2 eqn to use
I think the Cu and NH3 should directly find from the data booklet
2Cu + O2 + 2h20 + 8NH3 --> 2[Cu(NH3)4]2+ + 4OH-
thanks ultima your chemistry wisdom has benefited society haha
Last question, for the Cu taking long time to oxidize, only because CuO is formed ah ? no other possible explaination ?
Originally posted by ArJoe:Hi, for the heterogeneous question, i wrote partially filled 3d orbitals, reactant adsorbed onto catalyst surface, form temporary bonds, weaken bonds between reactant molecule, lowee activation energy, increase reactant concentration by bringing them closer. Frequency of effective collision rises.
For the cu and k qn, i quoted ie values, then said cu have higher nuclear charge and shielding effect, the additional 3d electrons provide shielding effect which largely nullifies the increase in nuclear charge, cu have higher effective nc, valence electrons more strongly attracted to nucleus, less easily oxidised
For cu reacting with acid, is it cu becoming cu+ or cu2+?
and can no2 be causing global warming? I thought respiratory isnt acceptable because they said environment?
Heterogenous-standard explanation
Cu and K- quoting probably gives free marks but then your explanation later should follow on what you quote. For example, if you quote I.E then your explanation should be on why lower I.E higher reactivity for K compared to Cu, but if you chose the otherwise option and decided not to quote from data booklet and instead talk about nuclear charge etc, then it should also be fine. But you cannot quote one thing and explain about another thing.
I would think Cu+ E value is 0.52 whereas the Cu2+ is 0.3something so Cu can be oxidised to either, its probably the safest to write both in and say E cell <0
Its not respiratory that is the environmental effect, its the photochemical smog. And they should accept global warming+acid rain as well as they are all valid
Originally posted by ArJoe:Hi, for the heterogeneous question, i wrote partially filled 3d orbitals, reactant adsorbed onto catalyst surface, form temporary bonds, weaken bonds between reactant molecule, lowee activation energy, increase reactant concentration by bringing them closer. Frequency of effective collision rises.
For the cu and k qn, i quoted ie values, then said cu have higher nuclear charge and shielding effect, the additional 3d electrons provide shielding effect which largely nullifies the increase in nuclear charge, cu have higher effective nc, valence electrons more strongly attracted to nucleus, less easily oxidised
For cu reacting with acid, is it cu becoming cu+ or cu2+?
and can no2 be causing global warming? I thought respiratory isnt acceptable because they said environment?
Didn't talk about partially filled 3d orbitals but did mention the rest hope its enough... And I think is to Cu2+ since its +0.34V and less positive than Cu+ half cell +0.52V so preferentially oxidised to Cu2+, not sure though...
And I didn't draw the bonds on in the draw ligand question i.e I didnt draw out the COO as O-C=O, just left it as COO, can?