Chemistry: Post your doubts here!

[MiniSacBall]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_qp_1.pdf Question 12

Well bro as far as my mind goes, it is D because they only said that 1 mole of the elements only. Not a certain mass (g). So According to the equation moles= Mass/Mr. If you find mass of the elements through this equation. You will find that we are burning more S than Al than Mg. So of-course burning an element in more mass requires more oxygen. Thus the answer is D.
If you have more doubts post them, i will try to help. And try to become more active in this thread specially
Hope this helps .

 

[sidbloom1995]

In NMR spectroscopy, what is an M+4 peak and i have a question regarding it that i need explanation on
it's from o/n 11 p41 q7 part c (iii)

 

[MiniSacBall]

AoA, I have one question, Will we get Periodic Table with the pp 1,2,3. Or with which papers will we get the periodic table. I am in AS. So please help me <3

 

[xhallay]

Would you like to mention the full question please, there must be more added to this question. You just can't tell it simply that it is this element or this. Well All the nitrates in Group 2 undergo thermal decomposition to give the metal oxide, nitrogen dioxide and oxygen. So i just can't simply say that it is Mg, Ca ...etc. Also as you go down the group, these metal nitrates become more stable to heat. So you need to heat Ca more than Mg. Because Ca is below Mg, thus it is more heat stable than Mg.

Hope this helps ,
I am As student so i have told you what i have learnt, and that it supported the question.

AoA, the Q is: a 5 gram mass of anhydrous group 2 metal nitrate loses 3.29 grams in mass on strong heating. which metal is present.
a) Mg b) Ca c)Strontium d) barium
This is whats all written in the question.
Thankyou.

 

[ahmed abdulla]

Paper 5 .
Does construction line mean drawing two lines to get two corresponding points on the line and hence find gradient ?
in the question posted , if we got gradient as 0.26 , how do we find the x value using the masses ?
This question is from mj2007

 

[chocolate_girl]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w07_ms_31.pdf
Can any1 please answer question 1 (e) part?

 

[Tanvir Azad]

Guys help me out... The question is: " Write down the reactant and conditions of these reactions."

 

[daredevil]

Can anyone confirm the equation of halogenoalkanes with ammonia

CH3Br + NH3 --> CH3NH2 + HBr


^is this right???

 

[Tanvir Azad]

Can anyone confirm the equation of halogenoalkanes with ammonia

CH3Br + NH3 --> CH3NH2 + HBr


^is this right???

yes, its totally correct.

 

[daredevil]

yes, its totally correct.

Thanks a bunchh

 

[Hassan Ali Abid]

Can anyone confirm the equation of halogenoalkanes with ammonia

CH3Br + NH3 --> CH3NH2 + HBr


^is this right???

yes this is ryt ....

CH3-Br + H-NH2 ------> CH3-NH2 + H-Br .. ( try to memorise like this so then it becomes easy to remember the equations )

 

[mahabaloch]

You could look for notes online to understand the concept. Finding isomers is not that hard. Or you could copy a few of those questions and we might be able to help you.[/quote]




yea ok thanks

 

[BreakingBad]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_ms_5.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_5.pdf
can anyone kindly explain Q1 part c,d,e,f and post the diagram for c
thnx in advance

Sorry for being late but here goes:

c) Drawing and uploading the diagram would be a real drag so i would like to use this image to explain:

The only thing you have to add to this diagram would be heat under the test tube which is necessary for the decomposition to take place. The reason we are using this apparatus (with water) is because we need to confirm out prediction in (b). We predicted that Equation 2 is correct according to the sequence and therefore we have to use our experiment to prove that 2 moles of CsNO3 must produce 1 mole of O2 instead of 4 moles producing 1. The water is required to dissolve NO2 produced so we get only O2 in the tube. I hope you can do the labeling. Remember that we have to show the volume that this cylinder can collect, say 500 cm^3.

d) Since we chose eqn. 2:
2 mol of CsNO3 gives 1 mole of O2
1 mole of CsNO3, therefore, gives 0.5 moles of O2.
Mol = V/24
V = Mol * 24 = 12 dm^3

e) Since we chose eqn 2:
1 mole of CsNO3 gives 0.5 moles of O2.
1mol = 0.5mol
mass/Mr = 0.5/12
mass = 0.5/12 * 195 = 8.125 g

The reason i got this answer is because i assumed the max volume of the cylinder to be 500cm^3 = 0.5 dm^3 previously. This means for a 0.5 dm3 cylinder, we get 8.125 gms. You can use this ratio to confirm that your answer respective to the volume you took is correct.

AoA, I have one question, Will we get Periodic Table with the pp 1,2,3. Or with which papers will we get the periodic table. I am in AS. So please help me <3

It will be given with 1 and 2. 3 will consist of Quantitative Analysis tables only. The necessary Mr or Ar values will be given in the question if need is there.

AoA, the Q is: a 5 gram mass of anhydrous group 2 metal nitrate loses 3.29 grams in mass on strong heating. which metal is present.
a) Mg b) Ca c)Strontium d) barium
This is whats all written in the question.
Thankyou.

M = Metal
The equation goes something like:
Mg(NO3)2 ==> MgO + 2NO2 + O2
1 mol of Metal Nitrate gives 1 mole of Metal Oxide.
Moles = Mass/Mr
Use this equation to calculate the moles of both nitrates and oxides of the 4 metals. Mass of nitrates is always 5 and mass of oxides is always (5-3.29) = 1.71g.
The one with the mol ratio closest to 1:1 would be the answer.

Paper 5 .
Does construction line mean drawing two lines to get two corresponding points on the line and hence find gradient ?
in the question posted , if we got gradient as 0.26 , how do we find the x value using the masses ?
This question is from mj2007
View attachment 35463

No, in this case, you don't have to find the gradient. You simply have to use the construction lines to get coordinates of one point on the line, say (4.2, 1.1).
Moles of Hg = mass/mr = 4.5-1.1/201 = 0.015
Moles of Cl = mass/mr = 1.1/35.5 = 0.3
Mol ratio = 1:2
Therefore, molecular formula = HgCl2

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_ms_31.pdf
Can any1 please answer question 1 (e) part?

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?

View attachment 35481 Guys help me out... The question is: " Write down the reactant and conditions of these reactions."

1) Reagent: Acyl Chloride
Conditions: Reflux and anhydrous condition.

2) Reagent: Acyl Chloride
Condition: Anhydrous.

Can anyone confirm the equation of halogenoalkanes with ammonia

CH3Br + NH3 --> CH3NH2 + HBr


^is this right???

Yes.

 

[Jie Xi]

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

 

[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.