Chemistry: Post your doubts here!

[Student12]

QP http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q 4, 11, 14 ? Can someone xplain & solve ?

QP http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
MS http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_ms_1.pdf
Q2, 6, 13, 15

Q-6, 8, 9, 10, 18, 25, 35
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_ms_11.pdf

PLEASE explain these Q's.

Its the 2nd or the 3rd time i'm posting them. Some one please Help me out

 

[umarashraf]

hi this is the first time that i post any thing on xtreme but i have a question can some one explain for me why question 11 m\j 2010 variant 12 is A because im confused

I HOPE GOOD LUCK FOR ALL OF U GUYS and THANKS...

mate its is a mere application of Lechatlierz principal... HYber process is an exothermic one... so the graph will temp will show more production of NH3... and increase in pressure will also increase the production of NH3......

 

[thunderingthunder]

hi this is the first time that i post any thing on xtreme but i have a question can some one explain for me why question 11 m\j 2010 variant 12 is A because im confused

I HOPE GOOD LUCK FOR ALL OF U GUYS and THANKS...

The percentage yield increases with an increase in temperature and pressure hence at 400c the %age yeild will be greater than that at 500c..
Hope this helps

 

[umarashraf]

The percentage yield increases with an increase in temperature and pressure hence at 400c the %age yeild will be greater than that at 500c..
Hope this helps

yield increases with an increase in temp...??? so u think 400 is a greater temp than 500...????

 

[KurayamiKimmi]

hi this is the first time that i post any thing on xtreme but i have a question can some one explain for me why question 11 m\j 2010 variant 12 is A because im confused

I HOPE GOOD LUCK FOR ALL OF U GUYS and THANKS...

see for Haber's process the equation is
N2+3H2=2NH3
and the forward reaction is exothermic.So the factors that increase the yield of ammonia are HIGH pressure and LOW teperature
so a temperature of 400 C will give you a better yield of ammonia than 500 C so the answer is not B and C and we are left with A and D.
since the yield will increase with HIGH pressure, we choose A because it shows that the yield is increasing with higher pressure Therefore answer is A- hope that helps ^_^

 

[KurayamiKimmi]

can anyone pretty please help me with mass spectrometry questions ^_^?
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

answer question number 2 please

 

[user]

I dont get it but A and B are also Halogenoalkanes? why isnt it B ?

sorry I meant only tertiary halogenoalkanes undergo SN1 mechanism... sorry missed out the word..my mistake..

 

[user]

Assalam-o-alaikum wr wb!

need help with these questions plz..

 

[freezingfires]

to make the alcohal a chiral one as well we can use minimum 7 Carbons....


CH3
!
C2H5 -C-OH
!
C3H7

these are six Carbons.... hope you understood mate...

Thanks a lot that really helped....

 

[hmlahori]

Q6) what i think is because, Nitrogen's molecule has more no. of electrons than the hydrogen molecule, therefore it's gonna have stronger vanderwaals forces than H, so as the intermolecular forces increase the gas is more likely to deviate from ideal gas behaviour.

Q11) ok, here just use algebra. we know that the no of moles of reactants initially is 1.
The mole ratio of the reactants and products is 1:1
therefore at equilibrium lets assume that x no of moles reacted. so now the moles of ethanol and ethanoic acid are 1-x and 1-x. on the products side since x moles reacted, to the moles of water and ethyl ethanoate are x, and x.
Now put it into the Kc equation:
(1-x)^2 ÷ x^2 = 4
square root both sides to make it easier.
now (1-x) ÷ x = 4
solve it ull get 2/3.

Q21) firstly is is cis form so its either A or C. haha thats it. i dont know, this is what the examiner report says:
''Presumably many of the former group did not appreciate that
the formation of a ring system has the same effect on the C:H ratio of the molecular formula as does a
double bond.''

Thanks that was really helpful! As for question 21 i'll post it again and see maybe someone knows how it is 5 bonds not 6.
But thanks anyways and gud luck in all exams!

 

[hmlahori]

Can anyone explain this question?​

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_11.pdf​

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_er.pdf​

Q21 How does the compound have 5 double bonds. I counted 6(one in the side chain and 5 in the cyclohexene ring due to presense of just one hydrogen in it.)​

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

please explain the ans to question 12 ^^

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

ans to question 16

 

[trgirl]

for question 11) try balancing out the reaction,in option d) you may see on the left side total number of oxygen atoms is 108 but on the right side its just 18 so the answer D is obviously wrong !!

for question 13)as the question as stated Ca(OH)2 which is basic so look out for acid which means proton donor...you can see HCO3- as the only proton donor !!

for question 31) read the question carefully,it states that the relative mass of 12C is 12 and the relative mass of particular chlorine is 72,so the question has asked what properties of an atom is always the same,note that it hasn't asked the similar properties between that atom of chlorine and carbon but what properties of an atom with different mass number of the same element are same,so the answer is atomic radius because isotope has different nucleon number and different atomic mass but the same radius !!!

for question 34) the question has asked which statement classify's Bronsted-Lowry definition,though option 3 is also right but the definition of Bronsted Lowry only states that acids are proton donor ,it doesn't states whether a compound is basic or not !!!

for question 35) see the option 2 first,as CaCo3 and MgC03 can react with acids which means they can react with acid impurities and see the option 3) metal oxides can't be reduced to metals which means option 3 is wrong so the answer is option 1 and option 2 !!

for question 37) option 1 and option2 are right but option 3 ) is wrong because whats the use of inserting oxygen in hydrocarbon for fuels,never heard or read about it before !!![/quote
what about 28,20,19

 

[mominzahid]

sorry I meant only tertiary halogenoalkanes undergo SN1 mechanism... sorry missed out the word..my mistake..

No problem i figured it out..
her can u check out 4 other questions i posted i need help with them.. see if you can answer. Thanks.

 

[hihi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

please explain the ans to question 12 ^^

it is C, because dotted line represents lower temp and solid-line curve higher temp and it temp is higher more molecules have sufficient enery to react(activation energy), colliding with each other faster so dotted- line curve must have higer peak

 

[hihi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

ans to question 16

Answer C, because relative molecular mass of Ca(NO3)2 is 164 so n=m/M (4.10/164=0.025 moles) n(Ca(NO3)2)=n(CaO) so mass of CaO = n*M= 0.025*56=1.40 g

 

[hihi]

need help with these, please:
34) A student puts 10 cm3 of 0.100 mol dm–3 sulfuric acid into one test-tube and 10 cm 3 of 0.100 mol dm–3 ethanoic acid into another test-tube. He then adds 1.0 g (an excess) of magnesium ribbon to each test-tube and takes suitable measurements. Both acids have the same starting temperature.
Neither reaction is complete after 2 minutes, but both are complete after 20 minutes.
Which statements are correct?
1 After 2 minutes, the sulfuric acid is at a higher temperature than the ethanoic acid.
2 After 2 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
3 After 20 minutes, the sulfuric acid has produced more gas than the ethanoic acid.
(answer: 1,2,3)


39) Use of the Data Booklet is relevant for this question.
In an organic synthesis, a 62% yield of product is achieved.
Which of these conversions are consistent with this information?
1 74.00g of butan-2-ol → 44.64 g of butanone
2 74.00g of butan-1-ol → 54.56 g of butanoic acid
3 74.00g of 2-methylpropan-1-ol → 54.56 g of 2-methylpropanoic acid
(answ: 1,2,3)

40)
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
(answ: 1only)

 

[KurayamiKimmi]

Answer C, because relative molecular mass of Ca(NO3)2 is 164 so n=m/M (4.10/164=0.025 moles) n(Ca(NO3)2)=n(CaO) so mass of CaO = n*M= 0.025*56=1.40 g

oh! i get it XD
thanks ^^

 

[mominzahid]

Assalam-o-alaikum wr wb!

need help with these questions plz..

View attachment 8481View attachment 8482View attachment 8483View attachment 8484View attachment 8485

In 38, 1 is the hydrolysis of Halogenoalkanes. elimination of HBr occurs and an alkene is formed.
Cant explain 40 confused abt it myself.. if u figure it out let me know too.
In 14, B is incorrect because across a period as atomic number increases melting point decreases. this is not shown by the graph. Cant be C because first ionisation energy shows a different trend eg S atomic number 16 has an ionisation energy less than P atomic number 15. Same is the case for D. That leaves A as the only sensible option.
Dont know abt 32 let me know aswell if u figure it out..
In 35 it is clearly mentioned that magnesium is the fuel and when magnesium is burned MgO is formed.. thus Mg(NO3)2 Cant be formed.