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Chemistry: Post your doubts here!

xxfarhaxx

xxfarhaxx

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DragonCub said:
Mercury level rises in the right-hand limb, this means that the pressure in R increases.
In 1, according to Le Chartelier's Principle, a rise in temperature would favour the forward reaction, thus the equilibrium position shifts closer to the products. In the reaction, every 1 mole of reactants forms 2 moles of products. As more reactants are converted to products, the total mole number (reactant plus product) in R gets larger, so the pressure becomes higher. 1 is correct.
In 2, since the mole number of reactants and products in the reaction is the same, where the equilibrium shifts to shall have no effect on the pressure since the total mole number stays unchanged. 2 is incorrect.
In 3, there is definitely no change since the two bulbs are filled with the same gas. 3 is incorrect.
Answer is D.
Click to expand...


bt shudnt u consider the volume of R???
 
Jaf

Jaf

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Scafalon40 said:
That is exactly why I mentioned carbonic acid.
Ca ions will remain in solution as ions, because in most cases Ca salts are soluble.
But CaCO3 is not soluble, is it?
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I still don't get why you're even mentioning carbonic acid. :/
If you've studied bio, you'd know it's usually lactic acid that that forms in the teeth. I feel I'm missing something?
 
H

Hinafatima

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please anybody can help me in Q#11 May /june 2011 component 12 with complete solution? any help would be highly appreciated.
 
Nikesh

Nikesh

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leosco1995 said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_11.pdf

November 2009, P11. Questions 19, 20 and 21 please. :)

In 21, I don't understand why there are 5 C=C bonds instead of 6.
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19)--> its A because C and D are automatically out as they both do not represent cyanate now in Ammonium cyanate charge of NH4 is 1 which means that charge on CNO must be -1.
20) D because Carbon atoms connect to CH3 (there are two such Carbon atoms) and to OH also posses chiral center as they are connected to 4 different groups...
21) its confusing 4 me too
 
tom ed

tom ed

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Nikesh said:
19)--> its A because C and D are automatically out as they both do not represent cyanate now in Ammonium cyanate charge of NH4 is 1 which means that charge on CNO must be -1.
20) D because Carbon atoms connect to CH3 (there are two such Carbon atoms) and to OH also posses chiral center as they are connected to 4 different groups...
21) its confusing 4 me too
Click to expand...
u seem to b doing the same paper....do u get q 40??..
 
tom ed

tom ed

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Zishi said:
2 and 3 should be correct. Because there are very large number of monomers combined in a polymer, the number of moles of a polymer will be much lesser than 1.
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the statement sounds very logical...that if 1 is wrong the answer is C...but i was just wondering that how is the 2nd statement correct?...10^-6??...
 
tom ed

tom ed

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Zishi said:
2 and 3 should be correct. Because there are very large number of monomers combined in a polymer, the number of moles of a polymer will be much lesser than 1.
Click to expand...
okk..after reading ur statement again...i hav understood a bit....thnk u!...and the video ..perfectly matches the situation.........:p
 
Nikesh

Nikesh

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tom ed said:
u seem to b doing the same paper....do u get q 40??..
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option 2 and 3 are correct as compound with molecular mass 88 can be formed using given conditions
1 is omitted because saturated refers to double and triple bonds both, however molecular mass of 88 could be obtained using double bonds but using triple bonds its never possible as carbon numbers is restricted to 4. I think this is the concept
 
tom ed

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Nikesh said:
option 2 and 3 are correct as compound with molecular mass 88 can be formed using given conditions
1 is omitted because saturated refers to double and triple bonds both, however molecular mass of 88 could be obtained using double bonds but using triple bonds its never possible as carbon numbers is restricted to 4. I think this is the concept
Click to expand...
thx but i guess the variant was different ....its 12.....thx anyway....:)
 
tom ed

tom ed

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Nikesh said:
wat does variant in this case refer to??
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the mcq paper u were solving is paper 11...i.e paper 1 ,first variant....
i did 12 ie..........paper 1 ,second variant...the questions are same but the order is different in both papers....
 
Nikesh

Nikesh

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tom ed said:
the mcq paper u were solving is paper 11...i.e paper 1 ,first variant....
i did 12 ie..........paper 1 ,second variant...the questions are same but the order is different in both papers....
Click to expand...

oh...no problem
whatever the order be
concept is same(y)
 
Scafalon40

Scafalon40

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Jaf said:
I still don't get why you're even mentioning carbonic acid. :/
If you've studied bio, you'd know it's usually lactic acid that that forms in the teeth. I feel I'm missing something?
Click to expand...
Option 3 says that Ca ions react with acids ( hence the equilibrium will shift to the right, decaying the tooth)
That statement is, theoretically, false. That is because any acid (such as sulphuric acid) will 'react' with the ions and the Ca salt formed will be soluble, hence there will be no overall change.
That is okay, but what if you add carbonic acid: there will be carbonate ions in solution, which will react with the Ca ion forming insoluble CaCO3. Hence the equilibrium will shift.
Yes, you are missing something: the syllabus assumes you do not study Biology.
 
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