Chemistry: Post your doubts here!

[Xylferion]

Can u plz tell me the third part as well!!
Thnx a lot for d help

X will be the most soluble spot in both solvents, since it's at the maximum values on both axes.

To find the most soluble amino acid besides this, you need to consider the spots that went the farthest on their axes as well as any spots that are on the straight line.

The spots that went the maximum are, (3,5) and (6,1), the one that's the highest up the straight line is (5,4).

If you multiply these numbers, you can find out which of them travelled the farthest.

3x5 = 15
6x1 = 6
5x4 = 20,

Hence the spot at (5,4) is most soluble in both solvents.

Note:- I do not take A2 chemistry, so I don't really know if there's an actual way you're meant to go about this. This is simply what made the most sense to me in terms of the way graphs work generally. ( This isn't a graph, but I considered it to be one )

 

[DESTROYER1198]

please help... why does the nucleus has more attraction in the cations than their atoms and why does the nucleus have less attraction in anions than their atoms

 

[ahmedish]

So

In excess NH3, a complex cation is formed [Ag(NH3)2]+

this works as tollens reagent right?

 

[ahmedish]

please help... why does the nucleus has more attraction in the cations than their atoms and why does the nucleus have less attraction in anions than their atoms

+ve ions are smaller as one electron shell is lost and the nuclear charge increases as it has to attract less electrons so ion is smaller.
-ve ions are larger as more electrons added which due to repulsion with already existing atoms expand to minimise repulsion.

 

[My Name]

http://onlineexamhelp.com/wp-content/uploads/2013/10/9701_s08_qp_2.pdf
question 3 part c iii

 

[asadalam]

http://onlineexamhelp.com/wp-content/uploads/2013/10/9701_s08_qp_2.pdf
question 3 part c iii

if kc increases with increase in temp that means forward is endo,as yield of right hand side will increase,hence increasing KC as KC is proportional to yield of forward reaction.

 

[NIM]

View attachment 52621

X will be the most soluble spot in both solvents, since it's at the maximum values on both axes.

To find the most soluble amino acid besides this, you need to consider the spots that went the farthest on their axes as well as any spots that are on the straight line.

The spots that went the maximum are, (3,5) and (6,1), the one that's the highest up the straight line is (5,4).

If you multiply these numbers, you can find out which of them travelled the farthest.

3x5 = 15
6x1 = 6
5x4 = 20,

Hence the spot at (5,4) is most soluble in both solvents.

Note:- I do not take A2 chemistry, so I don't really know if there's an actual way you're meant to go about this. This is simply what made the most sense to me in terms of the way graphs work generally. ( This isn't a graph, but I considered it to be one )

Thnx bro it really helped me

 

[Turki AbdulAziz]

Cis/Trans isomerism is basically just geometrical isomerism. It does not only apply to alkenes only, but to cycloalkanes too. They both have the formula CnH2n.

Try to think of the cycloalkane, as a ring placed flat on a surface. There are two planes, the top and the bottom one. So when you substitute an atom in place of the hydrogen, it really matters whether the atom is on the top or bottom plane.

For cyclopropane, since you're adding 2 chlorine atoms, there's two possible options. The halogen atoms are on the same carbon, or on two different carbons. Once you've finished drawing the structure for the atoms being on the same carbon, you have to consider the other situation.

When they are on two different carbons, they can both be on the same plane, or one on each. Similar to alkenes, when they're on the same plane, they're cis, and on different planes, trans.

----------------------------

For 4(f), you're going to be using your answer to (e).

If you look at the formula of your isomer, it's C4H4O4. In (f), it's C4H2O3.
Water has been removed, since two hydrogen atoms and one oxygen atom have been removed from the formula.

Now for this to happen, the OH group at the end of both -COOH groups, need to be close to each other, in order for this to happen under the presence of heat.
If you use your trans isomer, the -CO(OH) endings are far apart when compared to cis, so that's why trans does not react at the that temperature. ( 110 degrees )

The way it works is, the OH groups being close to other, one of the carbons ejects its OH group completely. With the OH- ion now with a lone pair, it attracts the H on the other -COOH group.

You end up with a molecule as such,

-COCH=CHCOO-

One carbons missing a bond and on the other end, oxygen is missing a bond. So the two end up sharing a bond, forming the cyclic compound.

View attachment 52615 -------> View attachment 52616 --------> View attachment 52617

Hope all of that made sense!

THANKS A LOT ! THAT HELPED SO MUCH!!

 

[Xaptor16]

okay its not an mcq question but i need help urgently!!
complete and balance the ionic equation for the reaction between the manganate (VII) ions and ethanedioate ions.
2 MnO4-(aq) + 5 C2O42-(aq) + ____ H+ ----> _______(aq) + 10 CO2(aq) + ____ H2O(l)
now my teacher taught us that to balance such equations, use the ionic equation from the data booklet for both the reactants and balance the number of electrons in each one so that they cancel out and add the two equations to get one complete reaction. now the problem is, i found an ionic equation (in a table by the name electrode reaction) for the managanate ions, but not for the ethanedioate ions.... help?!
if you need more information about the question, although i dont think anything else is relevant, its 9701/22/M/J/14 question 2(a)(ii)

 

[Metanoia]

ethanedioate ions is oxidised to CO2 and H2O (not found in the data booklet in this case).

 

[The Sarcastic Retard]

okay its not an mcq question but i need help urgently!!
complete and balance the ionic equation for the reaction between the manganate (VII) ions and ethanedioate ions.
2 MnO4-(aq) + 5 C2O42-(aq) + ____ H+ ----> _______(aq) + 10 CO2(aq) + ____ H2O(l)
now my teacher taught us that to balance such equations, use the ionic equation from the data booklet for both the reactants and balance the number of electrons in each one so that they cancel out and add the two equations to get one complete reaction. now the problem is, i found an ionic equation (in a table by the name electrode reaction) for the managanate ions, but not for the ethanedioate ions.... help?!
if you need more information about the question, although i dont think anything else is relevant, its 9701/22/M/J/14 question 2(a)(ii)

I usually do like:¬
Balance key element first ; 2Mn2+
Balance oxygen ; reactants have 28 and products have 20 so it needs 8 more, hence 8H2O
Balance hydrogen ; 16 H on product side hence 16 on reactants side.

 

[ahmedish]

Can someone explain ceramics to me? How does Al2O3 have covalent bonds? my book says aluminium oxide ceramics have giant molecular structure with a 3D network of strong covalent bonds?

 

[fantastic girl]

Assalamu Alaikum guys
can anyone tell me in Q4 the structure of D.....Why cnt it be R-CH(OH)CH3 ?
http://maxpapers.com/wp-content/uploads/2012/11/9701_w12_qp_43.pdf

 

[Xaptor16]

I usually do like:¬
Balance key element first ; 2Mn2+
Balance oxygen ; reactants have 28 and products have 20 so it needs 8 more, hence 8H2O
Balance hydrogen ; 16 H on product side hence 16 on reactants side.

oh okay, thanks!

 

[qwertypoiu]

Assalamu Alaikum guys
can anyone tell me in Q4 the structure of D.....Why cnt it be R-CH(OH)CH3 ?
http://maxpapers.com/wp-content/uploads/2012/11/9701_w12_qp_43.pdf

wa alaykum salaam
Firstly, I'm so mad I concentrated so much on this and then realised it was A2 afterwards...
I haven't done A2 so I may be wrong but it seems like compound D has to be a carbonyl compound, and the functional group you've given is not a carbonyl compound.

 

[Lola_sweet]

can someone tell me wht happens when a nitrile reacts with an acid?
The cynide ion gets replaced with wht?

 

[qwertypoiu]

can someone tell me wht happens when a nitrile reacts with an acid?
The cynide ion gets replaced with wht?

This is hydrolysis of nitrile, catalysed by the acid. Simply replace the nitrile group with carboxlic acid group.
Eg:
CH3CN ---------(HCl(aq), heat under reflux) --------> CH3COOH

 

[Bismillah jan]

I want inorganic chemistry short notes please........ Or some reaction pathways

 

[Bismillah jan]

I want short notes on inorganic trends and reactions... Will b thankfull....

 

[Boulus97]

Where can I find very good Chemistry paper 6B notes?

Please advise