Yatayyat
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I need some help answering a couple of these MCQ's!

1) https://imgur.com/Y9KDqvL
2) https://imgur.com/i9MQJ7s
3) https://imgur.com/ZDE9wHk

For 1) what I have thought is element Q is bonding with a sulfate ion SO4 2-

Hence element Q must have a +2 charge for it to be a compound with an overall neutral charge or else QSO4 would be a polyatomic ion instead. Does that mean an ionic bond exists between Q 2+ and SO4 2- ? If so I think that means that Q has to be a group 2 element as it has to donate 2 of its electrons for it achieve a full electron outer shell and also electrostatically attract to the negative sulfate ion But how do we find the electron configuration for Q?

For 2) I noted that the reaction is known to be an endothermic reaction in the forward direction because the enthalpy change value is positive. Therefore I know that any increase in temperature is one way of also increasing the yield of RM2 since this change would favour the product side to reduce temperature.

An increase in pressure also can increase the yield of RM2, since the reactants side is known to have 2 moles of gas but the product side has 1 mole of gas so any rise in pressure favours the product side i.e. yield of RM2 going up. That means options A and B can be crossed out as these both reduce the pressure and temperature not increase it like we want to for RM2 yield to rise. S

However I'm not too sure what change will happen with option C or D and how that affects RM2's yield? Could anyone please explain what changes will happen and why?

For 3) Not entirely sure how to identify what would be the best oxidising agent from a list of varying ions and elements. I know that an oxidising agent is something that is reduced itself because it is the substance that gains electron. So I think the substance is most likely to be easily reduced i.e. gain the most electrons is the better oxidising agent but how would I work this one out?

Any help would be fantastic and much appreciated. Thanks!
Last edited by Yatayyat; 1 year ago
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username3249896
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1. B because B is group 2 element and forms +2 ions.

2. C would increase the yield because equilibrium shifts to the right to oppose the change such that more product is formed
in D the pressure would halve, so the eqn shifts backwards to increase pressure.


3. You have already reasoned it out. Which one gains electrons most readily
Last edited by username3249896; 1 year ago
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Yatayyat
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(Original post by BobbJo)
1. B because B is group 2 element and forms +2 ions.

2. C would increase the yield because equilibrium shifts to the right to oppose the change such that more product is formed
in D the pressure would halve, so the eqn shifts backwards to increase pressure.


3. You have already reasoned it out. Which one gains electrons most readily
Okay for 1) I see how it is option B as this has a total of 20 electrons which is in fact calcium and this is group 2 element.

In 2) I see why it has to be option C now. With the effect you were stating when volume changes, does that mean volume is inversely proportional to pressure?

For 3) I can't seem to really know what features make a molecule or ion to attract more electrons to it? I know there is a trend in group 7 where as you go down the group the oxidising strength of each halogen decreases. If chlorine is above bromine in group 7, could we cross out options C and D definitely because we know that chlorine is a stronger oxidising agent than bromine? How do we know if the answer could be either option A or B now?
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username3249896
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(Original post by Yatayyat)
Okay for 1) I see how it is option B as this has a total of 20 electrons which is in fact calcium and this is group 2 element.

In 2) I see why it has to be option C now. With the effect you were stating when volume changes, does that mean volume is inversely proportional to pressure?

For 3) I can't seem to really know what features make a molecule or ion to attract more electrons to it? I know there is a trend in group 7 where as you go down the group the oxidising strength of each halogen decreases. If chlorine is above bromine in group 7, could we cross out options C and D definitely because we know that chlorine is a stronger oxidising agent than bromine? How do we know if the answer could be either option A or B now?
2 Yes. pV = nRT

3. Negative ions would not accept electrons readily since like charges repel. So cross out B and D. Now going down the group, the shielding effect increases and electrons are further from nucleus so smaller nuclear attraction. Halogens down the group accept electrons less readily and are poorer oxidising agents giving us the answer A
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Yatayyat
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(Original post by BobbJo)
2 Yes. pV = nRT
T
3. Negative ions would not accept electrons readily since like charges repel. So cross out B and D. Now going down the group, the shielding effect increases and electrons are further from nucleus so smaller nuclear attraction. Halogens down the group accept electrons less readily and are poorer oxidising agents giving us the answer A
Thanks this reason makes a lot sense now Thanks so much for your help!

PRSOM
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