Chemistry: Post your doubts here!

[Fardeen3342]

so just clarify something with me the 4.0 peak is due to ch-o yes ? because ms says just ch but just ch chemical shift isnt in that range

 

[Fardeen3342]

for b (ii) ms states that remaining is 10.8/1000 * 0.5 but isnt the amount reacted equal to that ???!

 

[qwertypoiu]

for b (ii) ms states that remaining is 10.8/1000 * 0.5 but isnt the amount reacted equal to that ???!

Imagine:
100 units of NaOH is reacted with SO2 and HCl. 90 units was consumed in this reaction. 10 units of NaOH remains in the solution.

This is called EXCESS NaOH was reacted with SO2 and HCl.


Now in real life we don't know that 90 units of NaOH reacted with SO2 and HCl. What we know is that we started with 100 units.

By doing titration with the remaining solution soup, we can know that 10units of NaOH REMAINED in the solution. This is the excess amount.


Using the above two information, we can do the magic: 100-10= 90 units of NaOH.

 

[Holmes]

oh how did u balance it?

Girl I am talking about the question to find molecular formula

 

[Holmes]

March 2017 Q6f(iii)


March 2017 Q7e(i)

Help me out any Chem Expert
anastasia grey113

 

[Zaki ali asghar]

for NMR, say that the peak splits into three, so there are 2 H on the adjacent carbon atom but what if there are two adjacent carbon atoms?

 

[Krypton36]

Anybody got the 9701 March 2018 Paper 42??

 

[Fardeen3342]

]

View attachment 63528
March 2017 Q6f(iii)

View attachment 63529
March 2017 Q7e(i)

Help me out any Chem Expert
anastasia grey113

its carbon environments so there are 3 different environments in the side chain and 4 different in the benzene ring itself

 

[Fardeen3342]

i cant understand please help

 

[anastasia grey113]

i cant understand please help

is it Nitrogen and sulfur?
for that u need to remember the test for sulfate ion
BaSO4 is insoluble unlike MgSO4

 

[Fardeen3342]

is it Nitrogen and sulfur?
for that u need to remember the test for sulfate ion
BaSO4 is insoluble unlike MgSO4

i got that part its the nitrogen and cl part how is overall charge of clo3 -1? m16 42 for your reference

 

[anastasia grey113]

i got that part its the nitrogen and cl part how is overall charge of clo3 -1? m16 42 for your reference

well it could be cuz do u remember the react ion of chlorine with hot NaOH to make NaClO3?
in it Cl has a charge of +5.
that's how its -1.

 

[anastasia grey113]

i got that part its the nitrogen and cl part how is overall charge of clo3 -1? m16 42 for your reference

but they said 'adjacent'groups
then how come its Cl and N?
theyr not from adjacent groups

 

[anastasia grey113]

i got that part its the nitrogen and cl part how is overall charge of clo3 -1? m16 42 for your reference

well i checked the mark scheme and it says sulfur and nitrogen

 

[Bilal hassan]

Hey guys, hope you guys are studying well for paper 4. I am wondering about this question, why when excess bromine is added, it only attaches to the phenyl group and doesn't add to the double bond by electrophilic addition. Is it a rule? Thanks and good luck

 

[Fardeen3342]

Hey guys, hope you guys are studying well for paper 4. I am wondering about this question, why when excess bromine is added, it only attaches to the phenyl group and doesn't add to the double bond by electrophilic addition. Is it a rule? Thanks and good luckView attachment 63538

The state of br2 should be liquid i think and not aq

 

[anastasia grey113]

Hey guys, hope you guys are studying well for paper 4. I am wondering about this question, why when excess bromine is added, it only attaches to the phenyl group and doesn't add to the double bond by electrophilic addition. Is it a rule? Thanks and good luckView attachment 63538

lol i dint quite get this either
my teacher also dint get the concept behind this
but he said that if there are two reactions ans theyre asking for one, the one with phenol should be considered

 

[anastasia grey113]

The state of br2 should be liquid i think and not aq

lol idky its stated like this here
but the bromine that is used is always dissolved in water
becuz if thats not done, bromine itself is a volatile liquid and would easily evaporate before all of the ethene reacts

 

[Zaki ali asghar]

https://papers.gceguide.com/A Levels/Chemistry (9701)/9701_s17_qp_42.pdf for Q3Biii why do we divide the answer in ii by 3? pls explain

 

[anastasia grey113]

https://papers.gceguide.com/A Levels/Chemistry (9701)/9701_s17_qp_42.pdf for Q3Biii why do we divide the answer in ii by 3? pls explain

Because in the previous part u calculated no. of moles of NaOH.
Now consider both the equations
2NaOH + SO2----> Na2SO3 +H2O
NaOH + HCl ------> NaCl + H2O
so u see that three moles of NaOH r required to react with one mole of SO2 and 1 of HCl.
So to produce 1 mole of HCl and of SO2 the RCOOH should be 1/3 of the NaOH.