Chemistry: Post your doubts here!

[qwertypoiu]

http://freeexampapers.com/A-Level/Chemistry/CIE/2007-Jun/9701_s07_qp_1.pdf
I need help in q) 9 , 12 and 13

9). Write Kc expression for both, and you'll see that the Kc for reaction 2 is the inverse and square root of the reaction 1 Kc, so the answer is 1/sqrt(2)
12) AlCl3, is a well known compound in our syllabus with slight ionic and slight covalency, and accounts for its amphoteric nature.
13) The Al is bonded to 4 stuff, and so they must be bonded tetrahedrally, so D.

 

[Xylferion]

Try writing the full equation and balancing it. Metal oxides react with acids to form a salt and water:
K2O + H2SO4 ---> K2SO4 + H2O.
This equation needs no balancing, and you can see therefore that the ratio of all the species is 1:1:1:1

Thanks

 

[Turki AbdulAziz]

9). Write Kc expression for both, and you'll see that the Kc for reaction 2 is the inverse and square root of the reaction 1 Kc, so the answer is 1/sqrt(2)
12) AlCl3, is a well known compound in our syllabus with slight ionic and slight covalency, and accounts for its amphoteric nature.
13) The Al is bonded to 4 stuff, and so they must be bonded tetrahedrally, so D.

Thanks a lot!
I understood 9 and 13, but for 12 I also thought it was AlCl3 until I checked the mark sheme which gave the correct answer as MgCl2

 

[qwertypoiu]

Thanks a lot!
I understood 9 and 13, but for 12 I also thought it was AlCl3 until I checked the mark sheme which gave the correct answer as MgCl2

Sorry my bad.
The question says: "Which chlorine compound has bonding that can be described as ionic with some covalent character?"
AlCl3 is actually a covalent compound, it's NOT ionic. I was getting confused by Aluminium OXIDE, which reacts with both acids and bases and is amphoteric.
NaCl when dissolved in water forms a solution with pH of 7. It forms Na+ ions and Cl- ions. It is completely ionic. AlCl3, being covalent (and not ionic), hydrolyses in water and forms Al(OH)3 and HCl. The resulting solution has a pH of 3.
MgCl2 can be described as ionic but forms a solution with pH of 6.5 when dissolved in water. The slight acidity is attributed to the slight covalent character.
So again, AlCl3 cannot be described as ionic, rather it is a covalent compound. So the right answer is MgCl2

 

[Turki AbdulAziz]

Sorry my bad.
The question says: "Which chlorine compound has bonding that can be described as ionic with some covalent character?"
AlCl3 is actually a covalent compound, it's NOT ionic. I was getting confused by Aluminium OXIDE, which reacts with both acids and bases and is amphoteric.
NaCl when dissolved in water forms a solution with pH of 7. It forms Na+ ions and Cl- ions. It is completely ionic. AlCl3, being covalent (and not ionic), hydrolyses in water and forms Al(OH)3 and HCl. The resulting solution has a pH of 3.
MgCl2 can be described as ionic but forms a solution with pH of 6.5 when dissolved in water. The slight acidity is attributed to the slight covalent character.
So again, AlCl3 cannot be described as ionic, rather it is a covalent compound. So the right answer is MgCl2[/QUOT

That helped a lot! Thank you.

 

[ashcull14]

NEED HELP :/

 

[Metanoia]

NEED HELP :/ View attachment 51588

Should be B. The chiral carbon is the rightmost carbon on that molecule. And when viewed individually, none of the C=C carbons are holding two identical groups. ( although this seems to be more correctly known as E/Z isomers rather than cis trans)

 

[ashcull14]

Should be B. The chiral carbon is the rightmost carbon on that molecule. And when viewed individually, none of the C=C carbons are holding two identical groups. ( although this seems to be more correctly known as E/Z isomers rather than cis trans)

i thought the same but there aren't any similar groups or elements present on the opposite sides of C atoms representing CIS or trans

 

[ashcull14]

had a problem in setting up the equation aswell

 

[Adnan Nurani]

please help me with question no. 2

 

[Adnan Nurani]

q2

 

[Adnan Nurani]

q2

 

[Metanoia]

View attachment 51591
had a problem in setting up the equation aswell

You can check the half equations provided in the data booklet.

 

[Metanoia]

please help me with question no. 2

Based on 1st equation, 1 mole of NaN3 produces 1 mole of Na and 1.5 moles of N2.

Based on the 2nd equation, the 1 mole of Na produced in the 1st reaction will then produce another 0.1 mol of N2.

 

[CЯeScɘnt]

Can anyone help me that how we can distinguish between primary secondary and tertiary helogenoalkens? ??
And secondly if anyone is having the organic notes for AS chem plz share them with me. .I desperately need them.

 

[awesomaholic101]

Can anyone help me that how we can distinguish between primary secondary and tertiary helogenoalkens? ??
And secondly if anyone is having the organic notes for AS chem plz share them with me. .I desperately need them.

http://www.chemguide.co.uk/mechanisms/nucsub/types.html

 

[Metanoia]

Can anyone help me that how we can distinguish between primary secondary and tertiary helogenoalkens? ??
And secondly if anyone is having the organic notes for AS chem plz share them with me. .I desperately need them.

Theoretically, one way would be to hydrolyze them with NaOH to form primary secondary and tertiary alcohols and then attempt to oxidize them with KMno4

1) tertiary would not be oxidized (no decolorization of KMnO4)
2) Primary would be oxidized to acid, secondary would be oxidized to ketone. Test with 2,4-DNPH for the ketone.

 

[CЯeScɘnt]

Theoretically, one way would be to hydrolyze them with NaOH to form primary secondary and tertiary alcohols and then attempt to oxidize them with KMno4

1) tertiary would not be oxidized (no colorization of KMnO4)
2) Primary would be oxidized to acid, secondary would be oxidized to ketone. Test with 2,4-DNPH for the ketone.

And can u plzzzzz share that dnph equation. .???

 

[Metanoia]

And can u plzzzzz share that dnph equation. .???

http://www.chemguide.co.uk/organicprops/carbonyls/addelim.html

 

[princess Anu]

what's wrong in 1