Chemistry: Post your doubts here!

[Awesome12]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf. Q9 ans A , q15 ans A , q17 ans D ,q19 ans D , q20 ans C q 35 ans B
Sorry they are a lot

I will answer 9
Electropostive is the act of the ion's attraction to the electrons. The more electropositive the metal, the greater the force of attraction, and thus the greater the reactivity. Conversely silver is less reactive and thus less electropositive

 

[Awesome12]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf. Q9 ans A , q15 ans A , q17 ans D ,q19 ans D , q20 ans C q 35 ans B
Sorry they are a lot

How is 35 B? I mean there are numbers only.

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf. Q9 ans A , q15 ans A , q17 ans D ,q19 ans D , q20 ans C q 35 ans B
Sorry they are a lot

Q15. Check that the oxidation state of silver before and after the reaction is +1, it means that it is neither oxidized or reduced. This effectively eliminates options B, C and D. silver chloride is insoluble and the silver complex formed is soluble.

Q9. less electropositve means less easily oxidised. It is harder to oxidise Ag (into Ag+ ions) than Cu into Cu2+ ions, so Ag remains in solid state while Cu dissolves.

Q17.
A: SO3 is acidic and NH3 is basic
B: There is a dative bond between N and 1 of the H in NH4+
C: Ionic bond between ammonium ion and sulfate ion
D: No change in oxidation state of the atoms

Q19. Hard to describe by typing, most easily missed out by students are the 3 chiral carbons that each contain a H which are not reflected in the diagram (check the "Y junctions")

Q20. all 3 C=C bonds are capable of cis-trans isomerism, so max isomers = 2^3 = 8

Q35.
1. Refactory linings require substances to withstand high temperatures
2. The carbonate will react with acidic gases to form solids and prevent the acidic gases from being released into the atmosphere.

 

[sadiaali]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Please anyone explain me Q40 , I cant understand a word

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Please anyone explain me Q40 , I cant understand a word

In direction of oxidation,

Primary alcohol functional group --> aldehyde function group --> acid functional group

secondary alcohol functional group --> ketone functional group

Q40.
1. (Correct) 1st compound aldehyde functional group is oxidised to 2nd compound acid group
2. (Correct) 2nd compound ketone functional group is reduced to 3rd compound alcohol group
3. (Correct) 1st compound alcohol group is oxidised to 2nd compound ketone group

 

[Metanoia]

I'm new to this forum, suppose I want to attach a diagram to explain some of the questions, do I need to host the image elsewhere or can I upload directly from my hard drive?

 

[Gehad Mohamed]

Hello! Can someone please explain how to solve Q 3 Q10 Q29 why not C ! Q39
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

 

[Gehad Mohamed]

Hello! Can someone please show me the angles by drawing them

 

[Metanoia]

Hello! Can someone please explain how to solve Q 3 Q10 Q29 why not C ! Q39
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

Q3. I don't have the data booklet at hand now, but you can look it up and add the 1st and 2nd IE of Al. Then see which of the 4 options give then same total value as Al.

Q10. D: Combustion of CH4 to CO2 and H2O is exothermic, so is the formation of N2 due to forming of triple bonds.

Q29. Option C is actually an ester bond on the left, not an acid functional group.

Q39.
Ethanol acts as base and gains proton to form CH3CH2OH2+
Conc H2SO4 acts as an acid and loses proton to form HSO4-
So statement 2 and 3 are correct

 

[Metanoia]

Hello! Can someone please show me the angles by drawing them

Qn is asking for bond energy, not bond angle.

I believe it should be C-Cl, but better check the data booklet to be sure.

 

[Gehad Mohamed]

Q3. I don't have the data booklet at hand now, but you can look it up and add the 1st and 2nd IE of Al. Then see which of the 4 options give then same total value as Al.

Q10. D: Combustion of CH4 to CO2 and H2O is exothermic, so is the formation of N2 due to forming of triple bonds.

Q29. Option C is actually an ester bond on the left, not an acid functional group.

Q39.
Ethanol acts as base and gains proton to form CH3CH2OH2+
Conc H2SO4 acts as an acid and loses proton to form HSO4-
So statement 2 and 3 are correct

Thanks alot

 

[Gehad Mohamed]

Qn is asking for bond energy, not bond angle.

I believe it should be C-Cl, but better check the data booklet to be sure.

Opps I misread the question thanks

 

[xXEleminatorXx]

Can any one explain how SO2 inhibits aerobic bacteria in preserving food?
And also the concept of dipole moment!

 

[Gehad Mohamed]

Hi ! Can someone please explain q 12 why no change in rate and hydrogen evolved when 40cm^3 is used ?! Concentration is more right so at least the rate will increase! !!
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

 

[kitkat <3 :P]

Hi ! Can someone please explain q 12 why no change in rate and hydrogen evolved when 40cm^3 is used ?! Concentration is more right so at least the rate will increase! !!
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

is the answer B ?

 

[Gehad Mohamed]

is the answer B ?

Yea it should be B

 

[kitkat <3 :P]

Yea it should be B

what s in the markscheme

 

[Gehad Mohamed]

Can any one explain how SO2 inhibits aerobic bacteria in preserving food?
And also the concept of dipole moment!

Use of so2 in food preservation : So2 since is bacteriostatic, is used in food preservation. Its reducing character when moist helps it to be used as a food preservative. They (so2 and sulphides) inhibit the oxidation of food compounds eg:unsaturated fats and also act as acids to restrict the growth of molds and aerobic bacteria.

Dipole moment is the shifting of shared electron pair towards more electronegative elements.
More electronegative elements like (F , O , N , Cl , S , P, Br)

Note that hydrogen and carbon are less electronegative elements and the difference between them are not much and is not significant.

 

[Gehad Mohamed]

what s in the markscheme

Its B now am asking why B not D

 

[kitkat <3 :P]

Its B now am asking why B not D

because the concentration of the limiting reactant is not changing