Chemistry: Post your doubts here!

[qwertypoiu]

It's says B as the answer.

Only B shows a p orbital.

p orbitals

 

[qwertypoiu]

View attachment 59588

Formation of ICl3 (s):

1/2 I2 (s) + 3/2Cl2(g) --> ICl3(s)

2 x Formation of ICl3 (s) :

I2(s) + 3Cl2(g) --> 2ICl3(s)


How to do this?

Easy.

Atomize: I2(s) ---> I2(g) [+38]

React: I2(g) + 3Cl2(g) ---> 2ICl3 (s) [-214]

Total = 38 - 214 = -176kJ

But this was 2 x Formation of ICl3(s)

So divide it by 2. -176/2 = -88kJ/mol

 

[qwertypoiu]

View attachment 59588

Oxidation number of N in:

NH4+ : -3

NO3- : +5

N2O : +1

So change from NH4+ to N2O is +4

And change from NO3- to N2O is -4

 

[Copy Cat]

Only B shows a p orbital.

p orbitals

Formation of ICl3 (s):

1/2 I2 (s) + 3/2Cl2(g) --> ICl3(s)

2 x Formation of ICl3 (s) :

I2(s) + 3Cl2(g) --> 2ICl3(s)


How to do this?

Easy.

Atomize: I2(s) ---> I2(g) [+38]

React: I2(g) + 3Cl2(g) ---> 2ICl3 (s) [-214]

Total = 38 - 214 = -176kJ

But this was 2 x Formation of ICl3(s)

So divide it by 2. -176/2 = -88kJ/mol

Oxidation number of N in:

NH4+ : -3

NO3- : +5

N2O : +1

So change from NH4+ to N2O is +4

And change from NO3- to N2O is -4

Jazak Allah Khairan

You're a life saver!!!

I still have a few more doubts,If possible can you please solve them............

 

[qwertypoiu]

Jazak Allah Khairan

You're a life saver!!!

I still have a few more doubts,If possible can you please solve them............

Bring it on

 

[Copy Cat]

 

[qwertypoiu]

View attachment 59589 View attachment 59590

X is not a strong acid. The pH is only 6.

An alkali that has a pH of 9 dissociates to produce some OH- ions. An acid that has a pH of 6 dissociates to produce some H+ ions.

Since neutral pH is 7, and 9 is further away from 7 than 6, that means X must be dissociating less.

 

[qwertypoiu]

View attachment 59589 View attachment 59590

CaCO3 and Ca(OH)2 both react with acids. KNO3 is a salt. It is a result of neutralisation, not a reagent.

 

[qwertypoiu]

View attachment 59589 View attachment 59590

NO can be oxidised to NO2 in the atmosphere pretty easily. SO2 can also be oxidised to SO3, especially since NO catalyses this reaction.

Unfortunately, CO is quite stable and won't turn into CO2 in the atmosphere. If that was the case, we wouldn't be complaining about CO, since it would be naturally depleted. Only the CO2 produced would be an issue due to global warming.

Oxidation of NO and SO2 to form NO2 and SO3 respectively doesn't solve any problems, since it still forms acid rain and weathers the buildings and destructs aquatic life.

 

[Saad the Paki]

So the 2016 syllabus for AS has somethings moved from A2 to As, namely carbon nanotubes and Buckminsterfullerene, infrared spectroscopy and iodofrom test. I have no where to practice questions from these so could anybody link some A2 papers having questions from these topics. Cheers

 

[The Sarcastic Retard]

Muammar:) Here you go.

 

[Konstantino Nikolas]

So the 2016 syllabus for AS has somethings moved from A2 to As, namely carbon nanotubes and Buckminsterfullerene, infrared spectroscopy and iodofrom test. I have no where to practice questions from these so could anybody link some A2 papers having questions from these topics. Cheers

Iodoform test I think A2 questions should be pretty much similar to the AS ones.
Question 5 of the specimen paper http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_y16_sp_4.pdf includes iodoform test.
Question 9 of http://theallpapers.com/papers/CIE/AS_and_ALevel/Chemistry (9701)/9701_w13_qp_43.pdf includes buckminister fullerene.

 

[Copy Cat]

CaCO3 and Ca(OH)2 both react with acids. KNO3 is a salt. It is a result of neutralisation, not a reagent.

NO can be oxidised to NO2 in the atmosphere pretty easily. SO2 can also be oxidised to SO3, especially since NO catalyses this reaction.

Unfortunately, CO is quite stable and won't turn into CO2 in the atmosphere. If that was the case, we wouldn't be complaining about CO, since it would be naturally depleted. Only the CO2 produced would be an issue due to global warming.

Oxidation of NO and SO2 to form NO2 and SO3 respectively doesn't solve any problems, since it still forms acid rain and weathers the buildings and destructs aquatic life.

Thanks a bunch.

 

[Iris Dylan Lane]

http://www.chemguide.co.uk/basicorg/isomerism/cholesterol.gif
How do I identify the chiral carbon atom?
Ty in advance..

 

[Konstantino Nikolas]

http://www.chemguide.co.uk/basicorg/isomerism/cholesterol.gif
How do I identify the chiral carbon atom?
Ty in advance..

Those numbers indicate the chiral carbons right? But I am pretty sure number 9 is not a chiral carbon ... 1 to 8 are though

 

[Iris Dylan Lane]

Those numbers indicate the chiral carbons right? But I am pretty sure number 9 is not a chiral carbon ... 1 to 8 are though

Yeah they do..but how am I supposed to know?

 

[Konstantino Nikolas]

Yeah they do..but how am I supposed to know?

Consider a single Carbon atom. First, make sure that the Carbon has four bonds connected to it. If not, then draw the extra bonds and add the hydrogen.
Let's take Carbon 1 as our example.

Now, consider the groups attached to that Carbon. There is an - H, - OH. That much is obvious. Then look at the GROUPS attached on both sides. A common mistake is to just consider the Carbon ATOMS attached on either side and claiming the carbon to be a non-chiral centre. When you see the group on one either side, they are different (You know this because if you split the whole compound at that carbon, the two sides will not be symmetrical). So 4 different groups attached to Carbon 1. Therefore, Carbon 1 is a chiral centre.

If you repeat this with every other numbered Carbon, you will realise that Carbon 1 to Carbon 8 are chiral. However, Carbon 9 is not a chiral carbon because it has two CH3 groups bonded to it.

Hope you understand.

 

[Konstantino Nikolas]

View attachment 59599

Consider a single Carbon atom. First, make sure that the Carbon has four bonds connected to it. If not, then draw the extra bonds and add the hydrogen.
Let's take Carbon 1 as our example.

Now, consider the groups attached to that Carbon. There is an - H, - OH. That much is obvious. Then look at the GROUPS attached on both sides. A common mistake is to just consider the Carbon ATOMS attached on either side and claiming the carbon to be a non-chiral centre. When you see the group on one either side, they are different (You know this because if you split the whole compound at that carbon, the two sides will not be symmetrical). So 4 different groups attached to Carbon 1. Therefore, Carbon 1 is a chiral centre.

If you repeat this with every other numbered Carbon, you will realise that Carbon 1 to Carbon 8 are chiral. However, Carbon 9 is not a chiral carbon because it has two CH3 groups bonded to it.

Hope you understand.

And the Carbons that are not numbered have either a double bond or have two Hydrogen atoms bonded to them. So they are fairly easy to eliminate from our list of chiral carbons.

 

[Iris Dylan Lane]

View attachment 59599

Consider a single Carbon atom. First, make sure that the Carbon has four bonds connected to it. If not, then draw the extra bonds and add the hydrogen.
Let's take Carbon 1 as our example.

Now, consider the groups attached to that Carbon. There is an - H, - OH. That much is obvious. Then look at the GROUPS attached on both sides. A common mistake is to just consider the Carbon ATOMS attached on either side and claiming the carbon to be a non-chiral centre. When you see the group on one either side, they are different (You know this because if you split the whole compound at that carbon, the two sides will not be symmetrical). So 4 different groups attached to Carbon 1. Therefore, Carbon 1 is a chiral centre.

If you repeat this with every other numbered Carbon, you will realise that Carbon 1 to Carbon 8 are chiral. However, Carbon 9 is not a chiral carbon because it has two CH3 groups bonded to it.

Hope you understand.

Yes I got it. Thank you so much. I really appreciate it
What if there were 6 C atoms in a ring, and one was bonded to CH3 and H? Is that C atom chiral?

 

[qwertypoiu]

Yeah they do..but how am I supposed to know?

Konstantino Nikolas already gave an excellent answer. I just wanna add one point.

To make it quick to find chiral carbons from a skeletal formula, you can find carbons from which at least 3 lines are coming out. The points (carbons) from which two lines are coming out (ie. The line just bent to form a vertex) must have 2 hydrogen atoms attached to it, so it could never be chiral. Furthermore, you should ignore any carbon attached to double bonds. This should help you find chiral centres quicker.

Of course, you still have to make sure there aren't two same groups attached to a carbon even if there are three lines coming out of it, like in the case of carbon number 9 in the above example.