Chemistry: Post your doubts here!

[Jie Xi]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Question 6 :why does x will higher??
Q10....thx very much!

 

[BreakingBad]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Question 31...can anyone explain why 2 is not the answer...?

1 is correct because the presence of water molecules delay the collisions reducing collisions per unit time (frequency) resulting in lesser rate.
2 is wrong because water doesn't reduce the total amount of effective collisions, it simply makes those collisions take longer.

Since there is no option of '1 and 3', the answer is '1 only' --> D

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Question 6 :why does x will higher??
Q10....thx very much!

6)
When the temperature is reduced, the peak has to get lower but the area under the graph must be kept the same. Therefore, Y falls and Z falls but the left side of the graph attains a greater height to keep the area same and hence, x increases. (They should have made it a little clearer though)

10)
Percentage/Mr can be used to get mol ratio. Find it for each element and then divide those moles with the smallest value of moles obtained. Multiply it so moles of calcium is 2 and the corresponding value of Al and Si moles will be answer.
Btw, an easier and time saving method to get the answer for this question would be to notice that their percentage and Mr of both Aluminum and Silicon are practically the same. Hence, their moles must be the same. The only option following that rule would be C which is the correct answer.

 

[abruzzi]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_42.pdf
I'm unable to answer the whole of qn 3 (c).. I'll really appreciate if someone could explain the solution. Pleaseee!
BreakingBad... and anyone else.
Thanks

 

[Jie Xi]

2 Equations involving four enthalpy changes are shown.

Na(g) → Na+(g) + e– Na(g) → Na2+(g) + 2e– Na(s) → Na(g)
Na(s) → Na2+(g) + 2e–

∆H= W ∆H = X ∆H = Y ∆H = Z

What is the second ionisation energy of sodium?A 2W B X – W C Y – W D Z – Y
help(

 

[Jie Xi]

Sulfur dioxide, SO2 , is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated with iodine, I2. In this reaction, one mole of SO2 is
oxidised by one mole of I2.
What is the change in oxidation number of sulfur in this reaction?
A +2 to +4 .
B +2 to +6
C +4 to +5
D +4 to +6.
How is the equation for the reaction??thx for help ya!

 

[MiniSacBall]

You are a hero Breaking bad. I am sorry for my stupid question but i am kind of confused will we be provided by periodic table, If yes in which papers. I am currently studying AS.

 

[chocolate_girl]

Sorry for being late but here goes:




It is a fact that the reaction that takes less time will have lesser error.
I cannot help with the uncertainties because i don't have the values for time obtained. Can't do the experiment at home now, can I?

My exp 1 value is 54.22s nd exp 2 value is 350.00s what will b the uncertainty then nd do we write error at reaction time space?

 

[Rammini]

I really need the chemistry revision guide book for AS and A level.... can anyone please email me a link or post it here ?? as ill be using it for a short period i just need it downloaded...
Would be MUCH appreciated if you can send it to me
Thank you
have a nice day.
Ps. i kinda need it ASAP

 

[♫Prince Shah♫]

I really need the chemistry revision guide book for AS and A level.... can anyone please email me a link or post it here ?? as ill be using it for a short period i just need it downloaded...
Would be MUCH appreciated if you can send it to me
Thank you
have a nice day.
Ps. i kinda need it ASAP

https://www.xtremepapers.com/commun...organic-inorganic-always-ready-to-help.31512/
here i had uploaded many chapters which are imp... look it out or tell me there if uh want more chapters other than that... Best of luck

 

[BreakingBad]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_42.pdf
I'm unable to answer the whole of qn 3 (c).. I'll really appreciate if someone could explain the solution. Pleaseee!
BreakingBad... and anyone else.
Thanks

c) i) The oxidation state of the molecule C2O4 is -2 because it forms a compound with Fe2+ as mentioned in the question, Fe(C2O4).
There are 4 oxygen atoms each with a valency of -2 and 2 carbon atoms with a valency of 'x' each.
Hence:
4(-2) + 2x = -2
x = +3

ii) We know that the valency of C2O4 is -2. We also know that the overall oxidation state of Fe(C2O4) when Fe(iii) is used is -3. Hence:

3(-2) + x = -3
x = +3

iii) To complete the diagram, you just have to add 3 ions of C2O4 to to the Fe in the centre. You might be confused because they have used skeletal formula for the ion but when you look closely, the corners represent the Carbon atoms in the C2O4 molecules.

iv) Just balance the equation like you would any other equation. Tip: Balance oxygen atoms last.

Sulfur dioxide, SO2 , is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated with iodine, I2. In this reaction, one mole of SO2 is
oxidised by one mole of I2.
What is the change in oxidation number of sulfur in this reaction?
A +2 to +4 .
B +2 to +6
C +4 to +5
D +4 to +6.
How is the equation for the reaction??thx for help ya!

The reaction will only occur if water is added.

SO2 + I2 + 2H2O --> H2SO4 + 2HI

S goes from +4 to +6, i.e. D

You are a hero Breaking bad. I am sorry for my stupid question but i am kind of confused will we be provided by periodic table, If yes in which papers. I am currently studying AS.

Nah, man. Just doing what anyone else would do. I would be very grateful if you people could pray for me as thanks, though.
P1 and P2 will have a periodic table. P3 will only have the quantitative analysis sheets but you don't have to worry, any required Mr or Ar values will be given in the question.

My exp 1 value is 54.22s nd exp 2 value is 350.00s what will b the uncertainty then nd do we write error at reaction time space?

Did you use a stop watch? How accurate was it? Like, what was the error limit, 0.1 or 0.01?

 

[sidbloom1995]

please help past paper question from may june 2013 p11
2. A mixture of 10 cm3 of methane and 10 cm3 of ethane was sparked with an excess of oxygen.
After cooling to room temperature, the residual gas was passed through aqueous potassium
hydroxide. All gas volumes were measured at the same temperature and pressure.
What volume of gas was absorbed by the alkali?

A 15 cm3 B 20 cm3 C 30 cm3 D 40 cm3

11. A solution of Sn2+ ions will reduce an acidified solution of MnO4 ions to Mn2+ ions. The Sn2+ ions are oxidised to Sn4+ ions in this reaction.
How many moles of Mn2+ ions are formed when a solution containing 9.5 g of SnCl 2 (Mr: 190) is added to an excess of acidified KMnO4 solution?

A 0.010 B 0.020 C 0.050 D 0.125

15. Element 85, astatine, is in Group VII. Concentrated sulfuric acid is added to sodium astatide. The mixture of products includes astatine, hydrogen astatide, hydrogen sulfide, and sodium sulfate. Which product is formed by the oxidation of one of the constituents of sodium astatide?

A astatine
B hydrogen astatide
C hydrogen sulfide
D sodium sulfate

plese reply
thank you

 

[abruzzi]

c) i) The oxidation state of the molecule C2O4 is -2 because it forms a compound with Fe2+ as mentioned in the question, Fe(C2O4).
There are 4 oxygen atoms each with a valency of -2 and 2 carbon atoms with a valency of 'x' each.
Hence:
4(-2) + 2x = -2
x = +3

ii) We know that the valency of C2O4 is -2. We also know that the overall oxidation state of Fe(C2O4) when Fe(iii) is used is -3. Hence:

3(-2) + x = -3
x = +3

iii) To complete the diagram, you just have to add 3 ions of C2O4 to to the Fe in the centre. You might be confused because they have used skeletal formula for the ion but when you look closely, the corners represent the Carbon atoms in the C2O4 molecules.

iv) Just balance the equation like you would any other equation. Tip: Balance oxygen atoms last.

Thanks a lot.. I appreciate it!

 

[Rammini]

no wait i need the download of the revision guide book...like the softcopy of it... ive got a hold of the extra notes as per chapter , thanks for the help.
BUT.
I'm looking for the softcopy of the revision guide for chemistry AS and ALevel cambridge.
pleaaaaassssseee help , i found several pdfs on this website but it won't download ((
HELP ME ASAP :"(

 

[♫Prince Shah♫]

no wait i need the download of the revision guide book...like the softcopy of it... ive got a hold of the extra notes as per chapter , thanks for the help.
BUT.
I'm looking for the softcopy of the revision guide for chemistry AS and ALevel cambridge.
pleaaaaassssseee help , i found several pdfs on this website but it won't download ((
HELP ME ASAP :"(

visit to my page for notes chemistry notes...https://www.xtremepapers.com/commun...organic-inorganic-always-ready-to-help.31512/

 

[Snow Angel]

Is this for as level chemistry as well?

 

[♫Prince Shah♫]

Is this for as level chemistry as well?

to whome are uh asking ?

 

[Snow Angel]

Anyone, it can be even you. So? Is it?

 

[♫Prince Shah♫]

Anyone, it can be even you. So? Is it?

obv.

 

[Snow Angel]

Yes or no

 

[♫Prince Shah♫]

Yes or no

yes.. jus go on to post.