Chemistry: Post your doubts here!

[periyasamy]

I chose A, why cant? Answer is B




Answer is D, I understand why it is structural isomer, but donno why osmotic pressure increase.

Answer is A.

Why??

Buddy,for 1st question i think the option a is not taken because ammonia is solluble in h20 soits conductivity in aqeous should be solluble.
For the 2nd question generally osmotic pressure increase when solute added to solvent.The addition of solute(h20) cause molarity to increase n the osmotic pressure increase as well
For the 3rd question in order if u want to find an answer in Hess law,it is vital to know two types of enthalpy change,as then only relation can be made.In this case option b and d is cancelled.Answer cant be option c because u need an extra value that is heat change of combustion of ch4,then only can do.
Hope it helps.....

 

[periyasamy]

Which pairs of homologous series have the same C:H ratio in their general formulae?
1 aldehydes and ketones
2 carboxylic acids and esters
3 alkenes and ketones

Answer is 1,2,3

Help :O

Buddy,easier way to do this is draw a basic structure for all options given that their carbon no is same.

 

[SIstudy]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w03_qp_1.pdf
Q2?? I don't get how to solve it :/ can sum1 pls explain it?

 

[SIstudy]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Q1?
how to solve it? I take alot of time when doin this :/

 

[Jessie N.]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w03_qp_1.pdf
Q2?? I don't get how to solve it :/ can sum1 pls explain it?

hope you can understand

 

[Jessie N.]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Q1?
how to solve it? I take alot of time when doin this :/

sorry for my handwriting lol

 

[Jessie N.]

Can someone explain these three questions to me pleaseeee :/

 

[periyasamy]

Hai,need help here.Ans is D.

 

[U7X0GXO]

Hai,need help here.Ans is D.

you haven't provided the options :/

 

[periyasamy]

you haven't provided the options :/

oops ,sorry boss.
A=1,2 AND 3
B=1 AND 2
C=2 AND 3
D =ONLY 1

 

[snowbrood]

oops ,sorry boss.
A=1,2 AND 3
B=1 AND 2
C=2 AND 3
D =ONLY 1

i thnk the answer is D
W should be magnesium oxide which is used as a refractory lining the furnace.
and X can be Calcium carbonate which when heated decomposes to Calcium oxide which then hydrated gives calcium hydroxide. calcium hydroxide is an alkali and cant decrease the ph of soil (all group 2 elements are alkalis so they cant decrease the ph)
u do know that calcium is more reactive than magnesium so option 2 and 3 are incorrect
W magnesium oxide has less mass as compared to calcium carbonate
so 1/23+oxide gives more number of moles than 1/40+carbonate
as number of moles=1/A if u increase A u decrease the number of moles and likewise

 

[periyasamy]

i thnk the answer is D
W should be magnesium oxide which is used as a refractory lining the furnace.
and X can be Calcium carbonate which when heated decomposes to Calcium oxide which then hydrated gives calcium hydroxide. calcium hydroxide is an alkali and cant decrease the ph of soil (all group 2 elements are alkalis so they cant decrease the ph)
u do know that calcium is more reactive than magnesium so option 2 and 3 are incorrect
W magnesium oxide has less mass as compared to calcium carbonate
so 1/23+oxide gives more number of moles than 1/40+carbonate
as number of moles=1/A if u increase A u decrease the number of moles and likewise

Thank u,boss.
Thanks for always helping.Hope u get awesome results ,surely u deserve it.

 

[periyasamy]

Can someone explain these three questions to me pleaseeee :/

For question 25,ans is d.This is because when dehydration occur there is 2 possibilty for the double bond to occur.I think u know this but why option d is selected is try to imagine the structure is rotated 180 degree n it will make sense.It is the same structure but just inverted the other way around.(I think that is the reason)
For question 31------ans should be a.if u do one by one for 1st option both have 3 unpaired p electron ,for option 2 both have three unpaired p electron and for option 3 both have 2 unpaired p electron.Just write them down n then check it.
For last question---i am not sure but i have seen someone answering that only the 1st option,ethanedioc acid is rite to cancel out the charge of 2+ of calcium ion....
Hope it helps.....

 

[periyasamy]

I need help for this question .I tried many times but cant get an answer for this.Thanks.Ans is c.

 

[Jinosupreme]

Which statements are true for an SN2 reaction?
1 One bond is broken as another bond is formed.
2 The formation of a transition state involves the collision of two molecules or ions.
3 A carbon atom in the transition state is bonded, either fully or partially, to five other atoms.

Answer is 1,2,3. Anyone can explain?

 

[periyasamy]

Guys another question here.Thanks .Ans for this is b.What is meant by the sentence"in which process is a transition element compound used rather than the element itself"

 

[periyasamy]

Which statements are true for an SN2 reaction?
1 One bond is broken as another bond is formed.
2 The formation of a transition state involves the collision of two molecules or ions.
3 A carbon atom in the transition state is bonded, either fully or partially, to five other atoms.

Answer is 1,2,3. Anyone can explain?

Yeah boss should be all 3.The sn 2 mechanism is substitution bimolecular whereby bond break and form at same time.So,unlike sn1 it occur at 1 go as both molecules collide at same time n this also causes the formation of 5 bonds(2 partially bond ,one that is going to break and another that is going to form.Look at the notes of halogenoalkane,it is sure explained better.

 

[snowbrood]

Can someone explain these three questions to me pleaseeee :/

 

[snowbrood]

Can someone explain these three questions to me pleaseeee :/

 

[snowbrood]

Guys another question here.Thanks .Ans for this is b.What is meant by the sentence"in which process is a transition element compound used rather than the element itself"

for A and D we use platinium for C we use Iron but for B we use vanadium oxide rather than vanadium so hope this answers ur question