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Chemistry: Post your doubts here!

S

smartangel

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hmlahori said:
Hey fellows need help with these paper 1 mcqs
Here are the links and questions.....
Thanks.......

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s05_qp_1.pdf Q13

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s07_qp_1.pdf Q12,16,18,22,34,40

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s08_qp_1.pdf Q8,14
Click to expand...

For 08. in q8 you just have to recall Boyle's Law and Charle's Law. its D. as per charles law volume is propotional to temp.
in 14.. you need to look at the periodic table. option B C D form ionic compounds. Aluminium, on the other hand is in group3 hence can form covalent compounds. like AlCl3.
Plese have a look at my questions in the previous post and see if you can help me out. thanks :)
 
smzimran

smzimran

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smartangel said:
May/jun 03 paper1 Q 2,13,29. PLEASE HELP!
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
Click to expand...
2.
B is the answer.
(There are 3 double bonds initially)
They are saying one of its side chains should be converted into a long chain with 2 double bonds still left, that means 1 double bond should be hydrogenated.
And they are saying two side chains should be converted into a long chain with 1 double bond, that means 2 double bonds should be hydrogenated in both (2 * 2 = 4 in total)
Total number of bonds that need to be hydrogenated are = 4 + 1 = 5
So, 5 moles H2 are needed.

13.
C is the answer.
In this case, for the mixture to be neutral, there can be two possibilities:
1. Both oxides are amphoteric
2. One oxide is acidic and the other is basic
Now, lets check,
A: Al2O3 is amphoteric and MgO is basic
B: Both are basic
C: Na2O is basic and P4O10 is acidic
D: Both are acidic
C matches the criteria so it is the answer

29.
C is the answer.
You should know H2SO4 (conc.) is needed for this reaction
And to purify ethene from any additional amount of acid added, an alkali is bubbled through to neutralise the effect of the acid
:)
 
Muhammad Bin Anis

Muhammad Bin Anis

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hmlahori said:
could you please explain Q 13 again.
i already know all that you explained
but why isnt the answer not magnesium because it is closest to aluminium in the periodic table
so that means its electronegativity must be most similar to aluminium.

and for question 38 the correct answer is A.
i just realized that option 3 (HOCH2CH2OH) which is a diol is formed when ethene is reacted with cold, dilute acidified potassium manganate.
Click to expand...

in Magnesium's case
U just go back so just decrease the e.n value
when u move up u increase it .
From Aluminium go back to magnesium and then up to beryllium
 
hmlahori

hmlahori

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smartangel said:
For 08. in q8 you just have to recall Boyle's Law and Charle's Law. its D. as per charles law volume is propotional to temp.
in 14.. you need to look at the periodic table. option B C D form ionic compounds. Aluminium, on the other hand is in group3 hence can form covalent compounds. like AlCl3.
Plese have a look at my questions in the previous post and see if you can help me out. thanks :)
Click to expand...

i understand question 14 but for question 8 why cant the answer be A because that also makes sense. pressure is inversely proportional to volume at constant temperature?
 
Amy Bloom

Amy Bloom

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Hello there!
I've a series of doubts which i would be grateful if you could clarify them for me & check my answers.

(1) For the Nickel-Cadmium cell, the electrode reactions are given below: [--> means "in equilibrium with"]
Cd(OH)2 (s) + 2electrons --> Cd (s) + 2OH-
NiO(OH) (s) + H2O (l) + electron --> Ni(OH)2 (s) + OH- (aq)
Make a summary of the cell.
My answer: NiO(OH) | NiO(OH)2 || Cd | Cd(OH)2

(2) What is the role of KOH (aq) in the Nickel-cadmium cell?
My answer: To provide the OH- ion for reaction to occur.

(3) Predict the change in Electrode potentials in cell of the Daniell cell of the concentration of (i) CuSO4 is increased and (ii) ZnSO4 is increased?

Request : Reply as soon as possible :)​
 
sumaiyarox:)

sumaiyarox:)

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can someone plzzz explain the reflux thing in brief....n also question 5e from paper 2 may june 10.??
plzzzzz
 
sumaiyarox:)

sumaiyarox:)

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what volume of oxygen ,measured at room temperature and pressure,is required for the complete combustion of 8.65g of H2S ?
plzz help..howz this done..??
 
smzimran

smzimran

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sumaiyarox:) said:
can someone plzzz explain the reflux thing in brief....n also question 5e from paper 2 may june 10.??
plzzzzz
Click to expand...
Heating under reflux means heating without having the risk of the liquid evaporating or splashing off the flask
A liebag condenser condenses the evaporaing liquid back into the flask
:)
A Request:
Plz post the link to your questions
 
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smartangel

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smzimran

smzimran

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smartangel said:
thanks a lot bro!! okay this might get annoying for you but since my chem is kinda bad so here"s one more question..Q20 0f the following paper.
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
such questions are there in almost every paper and i always get them wrong.. how exactly do we do them?
Click to expand...
I also have not been able to figure out a shortcut to such questions :(
Here are possible structures:
ClCH2 - CH = CHCl [2 isomers of this cis and trans]
CH3 - CCl = CHCl [2 isomers of this cis and trans]
CH3 - CH = CCl2
Cl2C - CH = CH2
ClCH2 - CCl = CH2
;)
 
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