Chemistry: Post your doubts here!

[xxfarhaxx]

mcq hlp!!!

o/n/10- q- 10,18,22

 

[XPFMember]

Assalamoalaikum wr wb!

Got some doubts in P1

 

[xxfarhaxx]

may-june 2010 qp 11 ,q.no , 29 and 30 ..please tell me how to solve these kind of problem,.

wel u gt to drw da structures fr each n evrythng n check i gues..

 

[alphabravocharlie]

Assalamoalaikum wr wb!

Got some doubts in P1
Got some doubts in P1

View attachment 8282View attachment 8283View attachment 8284View attachment 8285View attachment 8286View attachment 8287View attachment 8288View attachment 8289

25: First one: cracking, requires high temperature
2nd and 3rd: Substitution reaction, require heat
So D remains

37: Y is CO dude

20: no other option is right

 

[raiyanfarrukh]

I am not sure if this is the right way to solve it, but I got the right answer with it so..

C6H12 + 9O2 -> 6CO2 + 6H2O

So you have 6 moles of CO2 and 6 moles of H2O. P will absorb all of the mass of H2O, while Q will absorb of all of the mass of CO2. Their masses are 6(18) and 6(44) respectively, and the ratio will give you 18/44 = 0.41.

Thank u very much!!!

 

[raiyanfarrukh]

What are the bond angles in the PH3 molecule likely to be?
A) 90
B) 104
C) 109
D) 120

Question is Q7 from Winter 2004, http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_er.pdf

PH3 has 3 bonds and 1 lone pair, so I thought the bond angle would be 109. But the answer is 104, why is that?

Actually the right answer is 107 but as u can see there is no option with 107 so choose the option which is lower than that not higher!!

 

[xxfarhaxx]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

http://www.xtremepapers.com/CIE/Interna ... 3_qp_1.pdf

26....only secondary alcohols will give 1 oxidation product, i.e. ketone..
A. wrong coz its a primary alcohol (ths will gve aldehyde n a carboxylic acid)
B. its right cz 2ndry alcohol
C.not 2ndry thefr its wrong
D. its a tertiary alcohol..dsnt gve any products on oxidation

 

[Pals_1010]

Why is the answer D? Not C?

Shouldnt Sulphur form SO2 on complete combustion? This looks like SO3 was formed in D?

 

[xxfarhaxx]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

http://www.xtremepapers.com/CIE/Interna ... 4_qp_1.pdf
q. 20 and 26

ANS D
cz an intrmediate is formed (in A n B no intermediate frmed) n since da first step is slow da products hav lower energy than da reactants..
n da second step is fast the reactants hav mre energy than da reactants!!!!

 

[xxfarhaxx]

View attachment 8290


Why is the answer D? Not C?

Shouldnt Sulphur form SO2 on complete combustion? This looks like SO3 was formed in D?

y cnt da answ b A..a stedy increase??

 

[Pals_1010]

Mg + (0.5)O2 -------> MgO (No of moles of Oxygen used 0.5)

Al + (0.75)O2 --------> (0.5)Al2O3 (No of moles used 0.75)

S + O2 --------> SO2 (No of moles used 1)

I think in A the scale on the vertical axis wouldnt be good. Any idea?

 

[Student12]

why does argon not form a chloride ?

 

[xxfarhaxx]

Mg + (0.5)O2 -------> MgO (No of moles of Oxygen used 0.5)

Al + (0.75)O2 --------> (0.5)Al2O3 (No of moles used 0.75)

S + O2 --------> SO2 (No of moles used 1)

I think in A the scale on the vertical axis wouldnt be good. Any idea?

bt its da sme i all...if u c da increase in mols..it increases by 0.25..so y cnt it b A??

 

[Nikesh]

View attachment 8290


Why is the answer D? Not C?

Shouldnt Sulphur form SO2 on complete combustion? This looks like SO3 was formed in D?

ya answer is D, because there is formation of SO3 here
deduce reaction equation in each case and find number of moles of oxygen in each cases
you will probably find to be 0.5, 0.75 and 1.5

 

[Pals_1010]

ya answer is D, because there is formation of SO3 here
deduce reaction equation in each case and find number of moles of oxygen in each cases
you will probably find to be 0.5, 0.75 and 1.5

Yeah but how can SO3 be formed just by burning in excess oxygen?

 

[xxfarhaxx]

why does argon not form a chloride ?

cz it has a complete octet of electrons..(8 electrons in its outer shell)

 

[hmlahori]

Guys need help on these as quick as possible, exam's in four days!
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
http://www.xtremepapers.com/papers/...and AS Level/Chemistry (9701)/9701_w06_er.pdf

Q6 Why not B?
Q11 used a long method to solve it but ended up guessing the answer.
Q23 Why not A or D?​

 

[Pals_1010]

bt its da sme i all...if u c da increase in mols..it increases by 0.25..so y cnt it b A??

I know... Am confused but marking scheme says D

 

[xxfarhaxx]

hlp!!!!
12/o/n/10
Q- 10,18,22

 

[Pals_1010]

bt its da sme i all...if u c da increase in mols..it increases by 0.25..so y cnt it b A??

If the first division was 0.5 then the second division should be 1.0 then A isnt correct. As 1.0 moles of oxygen doesnt correspond to Al