Chemistry: Post your doubts here!

[studyingrobot457]

i need a help in this question why is it A?

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[Unknown202]

 

[Unknown202]

Now ?!

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[Hamnah Zahoor]

View attachment 62921

When ever two stages are involved in reaction its ethalpy profile diagram will have two humps in its graph .......as it is stated in the question X-Y is positive thus it will be endo and reactants will have low energy than the products....in Y-Z ethalpy change is neg thus its exo and reactants will have high energy than products as shown in option A

 

[Unknown202]

When ever two stages are involved in reaction its ethalpy profile diagram will have two humps in its graph .......as it is stated in the question X-Y is positive thus it will be endo and reactants will have low energy than the products....in Y-Z ethalpy change is neg thus its exo and reactants will have high energy than products as shown in option A

So it can't be B r8

 

[Hamnah Zahoor]

So it can't be B r8

No....no humps in the graph

 

[Unknown202]

K thx soo much

 

[MShaheerUddin]

 

[sweetiepie94]

https://www.xtremepapers.com/community/threads/as-level-chemistry-mcq-help.47789/ HELP HERE

 

[MnMz Mohammad-M]

2Al+Ba(NO3)2--->Al2O3+Bao+N2
Mole of Ba(NO3)2= 0.783/(261)=3x10^-3 mole
Mole of N2=mole of Ba(NO3)2= 3x10^-3 mole
1 mole--->24 dm^3
3x10^-3= 24x(3x10^-3)=0.072 dm^3
0.072dm^3=72 cm^3.
the answer is B. right?

The balanced equation should be 10Al + 3Ba(NO3)2 = 5Al2O3 + 3BaO + 3N2 , right? therefore we will get a different answer..
plz reply as soon as possible..

 

[Tigercub]

Can anyone help me please?
What is involved in the mechanism of the mechanism of the reaction between aqueous sodium hydroxide and 2-bromo-2-methylbutane?
A heterolytic bond fission, attack by an electrophile on a carbanion
B heterolytic bond fission, attack by an nucleophile on a carbocation
C homolytic bond fission, attack by an electrophile on a carbanion
D homolytic bond fission, attack by an nucleophile on a carbocation

 

[Metanoia]

Can anyone help me please?
What is involved in the mechanism of the mechanism of the reaction between aqueous sodium hydroxide and 2-bromo-2-methylbutane?
A heterolytic bond fission, attack by an electrophile on a carbanion
B heterolytic bond fission, attack by an nucleophile on a carbocation
C homolytic bond fission, attack by an electrophile on a carbanion
D homolytic bond fission, attack by an nucleophile on a carbocation

2-bromo-2-methylbutane is a tertiary halogenoalkane and will undergo sN1 'unimolecular' via carbocation reactions.



The C-Br bond will be broken heterolytically and a carbocation ion will be formed. The carbocation would then be attacked by the nucleophile (OH-)

 

[Metanoia]

The balanced equation should be 10Al + 3Ba(NO3)2 = 5Al2O3 + 3BaO + 3N2 , right? therefore we will get a different answer..
plz reply as soon as possible..

I don't have the context of the full question.

But in both equations, the ratio of Ba(NO3)2 and N2 happens to be 1:1. Therefore, it's a coincidence that the answers ended up to be the same.

 

[MShaheerUddin]

I don't have the context of the full question.

But in both equations, the ratio of Ba(NO3)2 and N2 happens to be 1:1. Therefore, it's a coincidence that the answers ended up to be the same.

Can you answer my question please?

 

[fahadhameedahmad]

Can you answer my question please?

are you talking about this question

 

[MShaheerUddin]

are you talking about this question

 

[Daveen]

Hey download this app called A level chemistry by overdose
available on playstore

 

[fahadhameedahmad]

lime stone is CaCO3
lime is CaO or Ca(OH)2
now all three would react with acids because acids react with carbonates (CaCO3) and bases (CaO/Ca(OH)2)

But old lime mortar effervesces (which means produces a gas), so this would be CaCO3 as it would produce CO2 gas with HCl

between A and D, D would be correct as water is present as well so quiklime would be Ca(OH)2

 

[Ayesha Amjad 22]

Hi Everyone I would like to post some very inportant notes for cie AS Level Chemistry. Download the notepad file. It contains the link to the website for Chemistry notes AS Levels only

 

[achaaa]

Question 2 b(iii)