Multiple Choice (3 Viewers)

[wyssm]

ok heres mine with justifications for those hard ones... ><

1A
2D
3C
4D
5B
6A
7B
8C
9A Cause resonance and coordinate bond plays no role in solubility and since dissolving in water is not a reaction so O3 being reactive is irrelevant and O3 is bent so clearly polar no matter what resonance

10C just remember the rules

11B ok this one i was not sure between B or D but i chose B as the question said bromine WATER which exists as HBr and BrOH so possible products would be bromopropanol or bromopropane.. and i chose 2- bromo be cause the hydrogen tends to go on the carbon with the most hydrogen which is C1 so Br would be on c2 If the question says bromine LIQUID then it would be D. But since A and B are both possible B is just more likely to occur than A then that would make both A and B the right answer which we know is not possible... so that was why i was not sure of B or D ... If you guys have any thoughts please add...

12D ok the term electrochemical activity... is weird but i would interpret it as the reactivity of the metal? the potential to be oxidised? which mean we must inverset the sign and rank it??? .. anyways i dont think this question is legit...

13C logically thinking about C would show that it is true while everything else is just rubbish ... also for those who chose D .. addition of KCl into solution will release Cl- which favours forward reaction hence will be more blue... so C

14C Ok the thing as 3 carbons so no branching possible so no methyl... so the isomers would only differ in the position of the Br and Cl atom... the possible combinations are 1Br-1Cl, 2Br-2Cl, 1Br-2Cl, 1Cl-2Br, 1Br-3Cl so 5.. noting that any combinations of 3-3 2-3 would result in the same molecule.

15A weak acids ionise completely when excess base are added.. so behave identically to a strong acid and require same amount of base to neutralise

16B the Salt produced when a weak acid vs strong base is basic hence pH>7 while salts of strong acids vs strong bases are neutral

17D use 108/2800 for number of moles combusted then multiply by molar mas of C5H12O u get 3.9999... rounds to 3.40 D

18A ok so by NaX the base is capable of accepting 1 proton so mol of HCL used= Mole of NaX in 20Ml then x5 for Mole in 100ml= 0.0122 hence 0.0122 moles of Nax weighs 1 gram then molecular mass = 1/0.0122 = 82.0g

19B this is easy? just mass>mole>volume
20B easy.. mass to mole to mass..

i reckon all right except 11. technically your right but i think hsc syllabus uses Br2 for bromine water not HBr. so D i think

 

[Gillywilly]

khorne's answers are 100% correct although i got 11 and 12 wrong :/
CONGRATS KHORNE! WOOOHOOOO

 

[friend177]

i think i got 14/20 lol oh well its my back up subject..somehow so far its better than economics wtf..

 

[jamesfirst]

I probably got 13/20 .... damn

 

[lpodnano]

1. a
2. d
3. c
4. d
5. b
6. a
7. b
8. c
9. a
10. c (as H+ reacts with CO3, Ba reacts with SO4 and then only CL is left)
11. d
12. D most negative voltage to most possitive
13. c
14. c 1,1 chloro bromo=3,3 chloro bromo, 1,2 chloro bromo, 1,2 bromo chloro, 2,2 bromo chloro, 1,3 bromochloro = 3,1 bromochloro
15. A or C is possible, but I think it is A, simply because if it didn't dissociate fully, we couldn't work out the concentration.
16. b
17. D 108/2800 = number of moles
18. a
19. b ( i think I put this down, I didn't mark an answer on my sheet)
20. b 200g of each you get 466.66+733.33, goes nicely.

I got exactly the same as you khorne. Except for 15 I got A.

 

[lpodnano]

Did everyone agree that Khorne received 20/20?

 

[matthewhearne]

I got 16/20 and made 3 stupid mistakes! Aghhhhhhhhhh!!!!!!!!

 

[LLButters]

I probably got 13/20 .... damn

Same here... :/

 

[abc123yoyo]

I got 16/20 and made 3 stupid mistakes! Aghhhhhhhhhh!!!!!!!!

Same here man i shodve gotten more then 2 hours sleep :3

 

[utanobeiiby]

i reckon all right except 11. technically your right but i think hsc syllabus uses Br2 for bromine water not HBr. so D i think

yeah it is more logical to be D but i was taught at my school to always think of Br2(aq) as an equilibrium with HBrO and HBr and the colour fade was due to a decrease in [HBrO] and [HBr] causing the equilibrium to shift right ... And hsc text books and study guides do this too so the question should've made clear what Bromine they meant.... But i think the wording of this year paper is ridiculous and totally ambiguous in many forms anyways .. like wth is electrochemical activity...

 

[Icee_tee]

umm just a quick question with q9. i think it's A but some other people think it's B, due to it's resonance structure. which one is right? kinda confused...

 

[zhuang281]

Not to boast but just to share info (I think my MC was all correct, but please correct me if i am wrong)
1.A
2.D
3.C
4.D
5.B
6.A
7.B
8.C
9.A (In answer to poster above, its A because its polar nature allows it to form dipole dipole bonds and thus is soluble)
10.C(Remember rules)
11.D(If it was BrOH and not Br2, none of the answers would be correct...think about it)
12.D( Had discussion with others and its D)
13.C
14.C
15.A(Defo 100% A. Think of it this way, when the current H+ ions produced the the ionisation of the weak acid is use, more will be produced to replace what is now missing. This will keep happening until all the 0.025x0.1 moles of acid will be used up. Same for the strong acid, it will keep being used up until all 0.025x0.1 moles of the acid is used up. Since its a 1:1 ratio for NaOH:Weak and NaOH:Strong, equal amounts will be used.
16.B
17.D
18.A(
19.B(99.95% sure these 3 questions are correct, went over them with a few friends)
20,B(

 

[yum135]

Not to boast but just to share info (I think my MC was all correct, but please correct me if i am wrong)
1.A
2.D
3.C
4.D
5.B
6.A
7.B
8.C
9.A (In answer to poster above, its A because its polar nature allows it to form dipole dipole bonds and thus is soluble)
10.C
11.D
12.D( Had discussion with others and its D)
13.C
14.C
15.A
16.B
17.D
18.A(
19.B(99.95% sure these 3 questions are correct, went over them with a few friends)
20,B(

I believe you are all correct indeed =]

i got 18/20 freaking silly mistakes! didnt have time to go back and check =[[

 

[Tasha270494]

Did anyone realise that 18 was in the past HSC paper???


Like exact wording. Well, it was in the Success One book and I was surprised when I saw it..

Yeah. They usually repeat questions that weren't answered well in the past..

 

[brettymaccc]

17/20.

 

[utanobeiiby]

11.D(If it was BrOH and not Br2, none of the answers would be correct...think about it)
(

I was thinking of HBr reacting with the alkene instead of BrOH it is possible to produce A and B if HBr is in molecular form (gas) i wonder if the reaction still occur if it was HBr(aq) because if it does then you would get both A and B being correct... Logically it would be D but technically the Board should not be using ambiguous terms like that as there is an obvious difference between WATER and LIQUID bromine..

 

[zhuang281]

True, and ive asked many chem teachers about this, they have all said assume bromine water = Br2

Quoting off wikipedia

For example, reaction with ethylene will produce 1,2-dibromoethane. Bromine also undergoes electrophilic addition to phenols and anilines. When used as bromine water, a small amount of the corresponding bromohydrin is formed >>>>>>as well as the dibromo compound.<<<<<<

 

[utanobeiiby]

umm just a quick question with q9. i think it's A but some other people think it's B, due to it's resonance structure. which one is right? kinda confused...

It's A! O3 is soluble because it is polar and it is always polar regardless of which resonating state it is in. this is because of the BENT SHAPE of O3, somewhat like water... and this shape is due to presence of lone pairs of electrons on the central atom and this has nothing to do with its resonance structure ... hope that is clear!

 

[utanobeiiby]

yeah cause the Bromine water would be in a kinda equilibrium where all reactants an products are present and any of them can react ==" oh well every text book and teachers said something different.. My teacher taught us to always think of bromine water as BrOh and HBr... thats why i chose B >< i literally circled both B and D and rubbed of D at the end cause i trusted my teacher >< Thats also the only multiple choice that i got wrong too!! >< dammit!

 

[Icee_tee]

It's A! O3 is soluble because it is polar and it is always polar regardless of which resonating state it is in. this is because of the BENT SHAPE of O3, somewhat like water... and this shape is due to presence of lone pairs of electrons on the central atom and this has nothing to do with its resonance structure ... hope that is clear!

thanks man! ALL CLEAR!!!