multiple choice...WTF? (1 Viewer)

[Dane-ger]

Q15: I'm fairly sure it's A.
n(I₂) = 0.5n(S₂O₃)
n(I₂) = n(MnO(OH)₂)

n(O₂) = 0.5n(MnO(OH)₂) = 0.5n(I₂) since n(MnO(OH)₂ = n(I₂)
but n(I₂) = 0.5n(S₂O₃)

.'. n(O₂) = 0.5 x 0.5 x n(S₂O₃) = 0.15

You're right. Some people probably thought thiosulphate was actually S406 instead of S₂O₃

 

[richz]

Q15: I'm fairly sure it's A.
n(I₂) = 0.5n(S₂O₃)
n(I₂) = n(MnO(OH)₂)

n(O₂) = 0.5n(MnO(OH)₂) = 0.5n(I₂) since n(MnO(OH)₂ = n(I₂)
but n(I₂) = 0.5n(S₂O₃)

.'. n(O₂) = 0.5 x 0.5 x n(S₂O₃) = 0.15

Then again, who knows if my reasoning is right.

mehhhhhhhhh

 

[Dumsum]

I'm seriously starting to think for question 1, after hearing everyone's reasoning, that both are as ambiguously correct as each other.

 

[~ ReNcH ~]

I'm seriously starting to think for question 1, after hearing everyone's reasoning, that both are as ambiguously correct as each other.

lol...let's just blame it on BOS and hope they either say B is correct p) or both B and D.

 

[Captain Gh3y]

The 0.15 seems very much correct to me; I went through all the equations backwards with the mole ratios and that's what I got.

i think question 1 is D, because if there are to many electrons to neutrons then there are also to many protons to neutrons becuase no. electrons = no. protons! that wuld mean that the N ratio is to small and the atom is unstable!
wat did u guys think?

Ions.

 

[~ ReNcH ~]

The 0.15 seems very much correct to me; I went through all the equations backwards with the mole ratios and that's what I got.



Ions.

Can radioistopes have charges?

 

[holla back girl]

lol...let's just blame it on BOS and hope they either say B is correct p) or both B and D.

i just don't get why theres such a debate on this...

isn't it a straight forward b?

I don't know about the quantum thingos that you physics people learn...but i don't think electrons has anything to do with radioactivity.

from my study...if its a radioactive isotope...then:
it has an atomic number greater than 83
or the ratio of neutrons to protons lies outside the zone of stability

 

[KFunk]

Using the definition from D you would probably call S^2- radioactive. The # of electrons =/= # of protons, also the nuclear properties of an element are independent of its chemical properties. At a stretch you could go for D but I would be inclined to say that it is incorrect.

 

[AreYouAlright?]

You guys are tools, Q15 is obviously A - 0.15 because 0.6mol of thiosulfate equates to 0.3 mol of I₂ gas which when put in equation 2 equates to the same moles of MnO(OH)₂ which when put in equation 1 equates to 0.15 mol of O₂ gas by mole ratios... geeze... n00bs

 

[Captain Gh3y]

Using the definition from D you would probably call S^2- radioactive. The # of electrons =/= # of protons, also the nuclear properties of an element are independent of its chemical properties. At a stretch you could go for D but I would be inclined to say that it is incorrect.

THANKYOU! I bet you'll all listen to him, just because he knows what he's talking about more often than I do.

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.

 

[~ ReNcH ~]

Using the definition from D you would probably call S^2- radioactive. The # of electrons =/= # of protons, also the nuclear properties of an element are independent of its chemical properties. At a stretch you could go for D but I would be inclined to say that it is incorrect.

So I'm guessing you put B?

 

[laserbrainz]

while I am here along with the rest of you looking at how I / you went, I have to relise that the BOS marks the paper, so i get to relax & realise that it's all over.

I am not against talking abot the q's (i already have been), but it is such a relaxing feeling doing what i have just jone ("it's over"). Faewell Chem. I'm glad I won't be doing it at uni (engineering all the way - Bring on the Physics)

Been nice competing with you. See you at uni.


Hence:

meh

 

[richz]

THANKYOU! I bet you'll all listen to him, just because he knows what he's talking about more often than I do.

lol captain, i know wat ur talking about

 

[Libbster]

for 1 i put b, as the isotope decays by emitting alpha 4/2He but d is ambigious because if u have too many electrons then u have the same no. of protons. oh well

i think 15 is b, but i put the wrong thing down cos when i was working backwards i wrote 0.6 instead of 0.3 on one of the atoms! damn!

14 is put d, cos the river source is nice and clean, then the limestone quarry could introduce calcium carbonate into the water, thus making a buffer and making the water neutral, and then the town has all crap n stuff in the water, thus there is a higher BOD.

 

[KFunk]

So I'm guessing you put B?

Very astute Rench . B was just a far safer answer IMO. It's the property of having to many neutrons and protons that makes a lot of the larger elements radioactive I think. I suspect it might be because the EM force has a long range so the electric field of each proton affects every other proton whereas the strong force is localised; so as the number of particles builds up you get a lot more force pushing on the fringe particles, making them more likely escape.

 

[~ ReNcH ~]

Very astute Rench . B was just a far safer answer IMO. It's the property of having to many neutrons and protons that makes a lot of the larger elements radioactive I think. I suspect it might be because the EM force has a long range so the electric field of each proton affects every other proton whereas the strong force is localised; so as the number of particles builds up you get a lot more force pushing on the fringe particles, making them more likely escape.

lol
Well, then I guess the only error I'll have to put up with is my stupid answer of D for Q5

 

[holla back girl]

i am beginning to think that this may be my first 15/15

=) please don't burst my bubble

 

[falltopieces]

Very astute Rench . B was just a far safer answer IMO. It's the property of having to many neutrons and protons that makes a lot of the larger elements radioactive I think. I suspect it might be because the EM force has a long range so the electric field of each proton affects every other proton whereas the strong force is localised; so as the number of particles builds up you get a lot more force pushing on the fringe particles, making them more likely escape.

I think B is the answer because I got this from my notes:

An unstable nucleus has one of the following:
1. surplus of protons
2. surplus of neutrons
3. surplus of mass or surplus of protons and neutrons

 

[richz]

lol
Well, then I guess the only error I'll have to put up with is my stupid answer of D for Q5

and the buffer q

 

[robbo_145]

B is the correct answer if by nothing else than elimination (ie its a badly worded question)
electrons have nothing to do with the stability of the nucleus