multiple choice...WTF? (3 Viewers)

[wanton-wonton]

me got
1.B
2.C
3.B
4.D
5.B
6.A
7.C
8.A (diprotic)
9.D (weak acid and conj. base)
10.C
11.A
12.B
13.C
14.A
15.A (follow the mole ratios)

If you follow mole ratios, wouldn't it be B?

 

[sarahsid]

yay.. sameness!!

me got
1.B
2.C
3.B
4.D
5.B
6.A
7.C
8.A (diprotic)
9.D (weak acid and conj. base)
10.C
11.A
12.B
13.C
14.A
15.A (follow the mole ratios)

whooooooo i got EXACTLY the same as yoo.. must mean something good.. riight? hahah
i feel great.. that exam was SO much better than expected!

 

[christina88]

Lol they were easy...but I dunno about question one...radioactivity isnt about too many neutrons and protons is about raito of neutrons: protons. So D is the answer because too many electrons = too many protons for the number of neutrons...I think anyway? My answers were: D, C, B, D, B, A, C, A, D, C, A, B, C, A, A...

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

:|

 

[Dumsum]

If you follow mole ratios, wouldn't it be B?

0.6 mol of thiosulfate
.'. 0.3 mol of iodine
.'. 0.3 mol of MnO(OH)₂
.'. 0.15 mol of oxygen

 

[Captain Gh3y]

sif it wasn't

B, C, B, D, B, A, C, A, D, C, A, B, C, D, A.

 

[sarahsid]

Lol they were easy...but I dunno about question one...radioactivity isnt about too many neutrons and protons is about raito of neutrons: protons. So D is the answer because too many electrons = too many protons for the number of neutrons...I think anyway? My answers were: D, C, B, D, B, A, C, A, D, C, A, B, C, A, A...

nah, a radioisotope is radio active if 1) proton : neutron ratio is too high, 2) proton : neutron ratio is too low, or 3) too many protons and neutrons in the atom.
unfortunately, electrons have nothing to do with it, but good reasoning! ehehe

 

[justchillin]

Actually on review, I think we are wrong...lol brain freeze. Because elements with atomic mass >83 are radioactive...so hence too many neutrons and protons. But can someone tell me this: isn't the defonition of an atom something neutral right - where number of electrons = number of protons...so D says that there are too many electrons for number of neutrons, ie too many protons for number of neutrons...making it radioactive???

 

[wanton-wonton]

No, fuck you all. The answer for 15 is B, I don't care what you all say.

 

[Dumsum]

Lol they were easy...but I dunno about question one...radioactivity isnt about too many neutrons and protons is about raito of neutrons: protons. So D is the answer because too many electrons = too many protons for the number of neutrons...I think anyway? My answers were: D, C, B, D, B, A, C, A, D, C, A, B, C, A, A...

Remember anything is radioactive if it's atomic mass is greater than 82, regardless of the neutronroton ratio... so I still think it's B.

 

[christina88]

nah, a radioisotope is radio active if 1) proton : neutron ratio is too high, 2) proton : neutron ratio is too low, or 3) too many protons and neutrons in the atom.
unfortunately, electrons have nothing to do with it, but good reasoning! ehehe

but isnt the number of electrons the same as the number of protons in an element? :|

 

[Captain Gh3y]

Electrons have NOTHING to do with radioactivity. Silly chemists and your electrons. So glad I never have to do this subject again.

 

[richz]

Actually on review, I think we are wrong...lol brain freeze. Because elements with atomic mass >83 are radioactive...so hence too many neutrons and protons. But can someone tell me this: isn't the defonition of an atom something neutral right - where number of electrons = number of protons...so D says that there are too many electrons for number of neutrons, ie too many protons for number of neutrons...making it radioactive???

radioactive substatances are ones which have a greater Neutron to proton ratio not proton to neutron

 

[justchillin]

I think they've made a boo boo in that question...because I can't see why its not D...although I know B is correct

 

[Captain Gh3y]

radioactive substatances are ones which have a greater Neutron to proton ratio not proton to neutron

No, if they're very small, it can be proton to neutron. Hence positron-beta decay.

I think they've made a boo boo in that question...because I can't see why its not D...although I know B is correct

Two reasons:

1. Consider the Manganese ion, Mn⁷⁺. It has less electrons, but does not become radioactive.

2. B is the most correct answer. Once you get past a certain sized nucleus, the coulombic force of repulsion is going to be greater than the residual strong nuclear force irrespective of the n: p ratio.

 

[Kd14]

I think I struggled a bit on some questions, hopefully I could get 10/15.

 

[richz]

No, if they're very small, it can be proton to neutron.

ok... never heard of that.

Out of interest do u have a source that i can read, that proves it. Im not trying to be arrogant, i just want to make sure and learn sumthing

 

[Captain Gh3y]

Physics. Quanta to Quarks topic.

 

[holla back girl]

No, fuck you all. The answer for 15 is B, I don't care what you all say.

i agree...15 is B

and going back to one...its b for sure

 

[richz]

ok, i'll have a read of it tonite, might as well study for it

 

[Dumsum]

If the BoS so determine... they may mark both B and D correct, or leave out the question entirely. I've heard of it being done before, and I've actually seen it happen in one of those Competitions run by UNSW.