multiple choice...WTF? (2 Viewers)

[richz]

D is correct because:

HCl is a strong acid, therefore its conjugate is an extremely weak base, too weak to actually act as a base.

H2SO4/HSO4 are an acid/base conjugate pair, but HSO4 is amphiprotic and is not guaranteed to act as a base.

H2PO4/PO4 are not a conjugate acid/base pair,

so that leaves only acetic acid/acetate ions, and of the 3 conjugate pairs, acetate ions are easily the strongest base.

argh... that q is so annoying me, im so pissed, my mind must have been somewhere else when i was reading this q, i thut they were asking for amphiprotic, argh...

 

[mattplaysguitar]

i got
B its deffinately B cause its too heavy to hold itself together
C
C wasnt sure how to work this out so divided 2676 by molecular mass, prolly wrong??
D
B
A
C
B it has to be B cause sulfuric ionises at 100% and using ph=-log[H+] u get 1. that right?
B this just looked familiar in buffers id seen b4. no idea really
C
A
B
C
C my teacher looked at this and she recons it has to be C, as do i
A worked through this with me teacher as well and we both agree on 0.15

12/15 maybe?? i did those practice ones from board of studies and picked 30 questions to do and got 15/30, so i tihnk this is an improvement. i tohught that they were really easy questions with a few mosre difficult ones to throw people, all in all, good mc happy

 

[punki_pixi]

Oops... well i lost a mark on the buffer question. I was pretty confident on the multiple choice at first but now I know I've got a few wrong now. You never really know how you went because its so easy to make simple mistakes and they try to trick you on purpose.. i usually manage to go pretty well but not sure about these ones.

Anyways, enough posting - time to study phys

 

[Abtari]

i got
B its deffinately B cause its too heavy to hold itself together
C
C wasnt sure how to work this out so divided 2676 by molecular mass, prolly wrong??
D
B
A
C
B it has to be B cause sulfuric ionises at 100% and using ph=-log[H+] u get 1. that right?
B this just looked familiar in buffers id seen b4. no idea really
C
A
B
C
C my teacher looked at this and she recons it has to be C, as do i
A worked through this with me teacher as well and we both agree on 0.15

12/15 maybe?? i did those practice ones from board of studies and picked 30 questions to do and got 15/30, so i tihnk this is an improvement. i tohught that they were really easy questions with a few mosre difficult ones to throw people, all in all, good mc happy

wth

how can 14 be C? i put down D, cos the river source has greatest dissolved oxygen...and pH is greater in town than river source so has to be D


and question 8 has to be less than 1.0 so it is A...
it is diprotic...the first rxn goes to completion, the second rxn doesnt...that means it is definitely more than 0.1 M concentration of H+ and hence less than 1 pH.

 

[Mz_mE]

Q8 i got b.. i did that -log[h] thingo too.. so i got exactly 1.. but i really doubt it woulda been that easy and from every1 elses answers i was wrong.. :S

Q14 i think is a... limestone has carbon dioxide which makes the water acidic.. so therefore ph would b low.. site 1 havin the lowest 5.2... river source is usually around 7? so thats site 2 ph of 6.9..and town was left over as site 3..

 

[punki_pixi]

ok, one more post then I'll study... For question 14 I couldn't remember much about dissolved oxygen or oxygen demand so I went by pH. Isn't the normal pH of water around 5.2? I remembered something like that cos it surprised me it was that low, or I could be making things up in my head. Anyways I decided that the site with 5.2 was the source, then the higher pH indicated the limestone place and the 6.9 was the pH after the town had made it more acidic than it was passing through limestone.
Well this is on my assumption that limestone makes it more basic but I'm likely to be wrong about that.

 

[Mz_mE]

ok, one more post then I'll study... For question 14 I couldn't remember much about dissolved oxygen or oxygen demand so I went by pH. Isn't the normal pH of water around 5.2? I remembered something like that cos it surprised me it was that low, or I could be making things up in my head. Anyways I decided that the site with 5.2 was the source, then the higher pH indicated the limestone place and the 6.9 was the pH after the town had made it more acidic than it was passing through limestone.
Well this is on my assumption that limestone makes it more basic but I'm likely to be wrong about that.

pure water ph is 7... the more acidic the lower the number the more basic the higher the number... 1(acidic)---7(water)---14(basic)

 

[punki_pixi]

Yeh but I thought water in lakes and rivers and stuff is slightly acidic due to the CO2 in the atmosphere and as its not really pure water. But yeh maybe I was looking for a trick in the question that wasn't actually there. And the limestone I thought made the water more basic, ie. higher pH, but I'm probably wrong about that too.

 

[thunderdax]

Answer to Question 14 is definately D:
River source has high desolved oxygen and is unpolluted, hence a low BOD. Also stable pH, hence site 2.
Limestone contains Calcium carbonate which is basic, so this is site 3(most basic)
The town can have industry which causes acid rain, lowering pH. Also, high BOD from pollution and sewage water.

 

[punki_pixi]

Yeh that makes sense, thanks for clearing it up

 

[Mz_mE]

limestone is made of carbon dioxide isnt it? if it is.. then according to bio c02 makes the blood acidic so im assumin it does the same to water?

 

[thunderdax]

I think you're thinking of limewater, which turns milky white when exposed to CO2. Neither limestone or limewater contain CO2.

 

[Mz_mE]

loolz yeh somethin like that.. my minds totally gone.. all the chem i learnt over 2 years is gone foreva.. lol

 

[Casmira]

1. b
2. c
3. b
4. b (this one was fucked)
5. d
6. a (guess)
7. c
8. a
9. d (guess)
10. c
11. a
12. b
13. d
14. d
15. b (guess)

 

[Rickdog]

question 1 - number of electrons has nothing to do with radioactivity

 

[Casmira]

question 1 - number of electrons has nothing to do with radioactivity

that wasnt aimed at me was it?

 

[midnight_magick]

I got exactly the same as you. Go us

Except I just realised that 14 is D. In the rush of the exam I read the lower pH as it meaning it was basic... good work Simon.

yay!! Great minds think alike!!! lols

 

[Pokute-san]

For Q11: Answer is actually B Iodine

Because:
The use of AAS has impacted the scientific understanding of trace elements because they discovered many different trace elements in soils which previously undetected. The trace elements lie in the range of 1 – 100 ppm. AAS demonstrated that trace elements are necessary for the proper functioning of organisms, and help work how these trace elements function. Trace elements includes Zn, Co, Cu, Ni

The trace elements lie in the range of 1 – 100 ppm. AAS demonstrated that trace elements are necessary for the proper functioning of organisms, and help work how these trace elements function. Trace elements includes Zn, Co, Cu, Ni, I.

u see there is I!

 

[mang]

that's exactly what i got for question 1.. D, same reasoning as u! evry1z got me worried here..
i got:
1D
2C
3B
4D
5B
6A
7C
8A
9D
10C
11A
12B
13C
14D
15A

:|

1.B
2.C
3.B
4.D
5.B
6.A
7.C
8.A
9.D
10.C
11.A
12.B
13.C
14.D
15.A
pretty much sameo cept Q1
do not question my answers or death will come to you all!
(i even put dots in between number and letter)

 

[mang]

For Q11: Answer is actually B Iodine

Because:
The use of AAS has impacted the scientific understanding of trace elements because they discovered many different trace elements in soils which previously undetected. The trace elements lie in the range of 1 – 100 ppm. AAS demonstrated that trace elements are necessary for the proper functioning of organisms, and help work how these trace elements function. Trace elements includes Zn, Co, Cu, Ni

The trace elements lie in the range of 1 – 100 ppm. AAS demonstrated that trace elements are necessary for the proper functioning of organisms, and help work how these trace elements function. Trace elements includes Zn, Co, Cu, Ni, I.

u see there is I!

your wrong!
you just are, dont question the superior logic of the goonhound