Chemistry: Post your doubts here!

[omarjaved619]

HELP!
Answer is C. I get what is going on in A and B. But could anyone help me understand C and D?

 

[omarjaved619]

Answer is A. I just dont understand 3

 

[sweet.sugar]

View attachment 45087 HELP!
Answer is C. I get what is going on in A and B. But could anyone help me understand C and D?

Look they said which one of them dsnt have lone pairs left
So has 5 electrons ryt, 3 will bond with H and since there are 2Na and 2 electrons are left each na would take one
Im nt sure though. Hope it made sense

 

[sweet.sugar]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q8-C Q10-C Q11-C Q19-A
Plz help

 

[Zepudee]

GUYSSSS. Gotta help me with this, PLEASEEE. hahahaha
Must be very easy for you guys!
Anyways, okay.
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_13.pdf
Q27 (C)

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_12.pdf
Q3 (B) Q8 (D) [ i guess all these answers correctly, but i dont understand why ]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_12.pdf
Q11 (A) [srsly no, what is this.]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q24 (B) , Q26 (A), Q30 (A)

THANK YOU SO SO MUCHHHHHH!! please help

 

[loveyuan]

for Q2
15/100 x 14 =2.1g of N
basically it is the mole : the 15/100
So, 0.15 mole
And 0.15/5 = 0.03 dm3

oh~ so no need to count mass of nitrogen it is ? how about question 6 ?

 

[SIstudy]

View attachment 45089

Answer is A. I just dont understand 3

3rd statement is a fact.
secondary alcohol ( alcohol where OH group is attatched to the carbon atom, which is bonded to 2 other carbon atom) is oxidized to ketone

 

[ZaqZainab]

GUYSSSS. Gotta help me with this, PLEASEEE. hahahaha
Must be very easy for you guys!
Anyways, okay.
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_13.pdf
Q27 (C)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_12.pdf
Q3 (B) Q8 (D) [ i guess all these answers correctly, but i dont understand why ]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_12.pdf
Q11 (A) [srsly no, what is this.]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q24 (B) , Q26 (A), Q30 (A)

THANK YOU SO SO MUCHHHHHH!! please help

I have only done w13 13
so
Q27
it is clearly an alcohol and a tertiary one as it is mentioned DOES NOT
Try making a tertiary alcohol WITH chiral center
so the center carbon can not be bonded to 2 CH3
the central carbon is bonded to OH,CH3,CH2CH3 and CH2CH2CH3

 

[Zepudee]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q8-C Q10-C Q11-C Q19-A
Plz help

Q8 whats the definition of enthalpy change of formation?
One mole of substance formed from its elements under standard conditions. So, its C! A and B definitely out since C in standard conditions should be in solid state.

Q10
Just look at Ca, Al and Si.
Do the empirical formula stuffs.
So, Ca= 14.04/40.1=0.35
Al= 14.17/27= 0.525
Si= 14.75/28.1=0.525
so you see, the mole ratio of Al and Si is the same, so you can straight eliminate B and D

Al and Si, both of them divided by 0.35 (cause it is the smallest mole ratio among three of them)
so 0.525/0.35=1.5
See the formula there, is Ca2 right? So, times 2. yeahhh it is 3. Hope you understand

Q11 it is posted somewhere like previous pages. or you just go and search google for the question. LOL SORRY trying to help but yeah, im rushing! WAIT I FOUND IT.
Moles of CO2=72/24000=0.003
moles of Al4C3= 0.003/3=0.001 (as ratio of Al4C3:CH4 is 1:3)
now mass of Al4C3= 0.001 into (27+27+27+27+12+12+12)=0.144g

Q19 idk whyyy

 

[SIstudy]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q21 (C)???
Q23 (B)???

 

[sweet.sugar]

Q8 whats the definition of enthalpy change of formation?
One mole of substance formed from its elements under standard conditions. So, its C! A and B definitely out since C in standard conditions should be in solid state.

Q10
Just look at Ca, Al and Si.
Do the empirical formula stuffs.
So, Ca= 14.04/40.1=0.35
Al= 14.17/27= 0.525
Si= 14.75/28.1=0.525
so you see, the mole ratio of Al and Si is the same, so you can straight eliminate B and D

Al and Si, both of them divided by 0.35 (cause it is the smallest mole ratio among three of them)
so 0.525/0.35=1.5
See the formula there, is Ca2 right? So, times 2. yeahhh it is 3. Hope you understand

Q11 it is posted somewhere like previous pages. or you just go and search google for the question. LOL SORRY trying to help but yeah, im rushing! WAIT I FOUND IT.
Moles of CO2=72/24000=0.003
moles of Al4C3= 0.003/3=0.001 (as ratio of Al4C3:CH4 is 1:3)
now mass of Al4C3= 0.001 into (27+27+27+27+12+12+12)=0.144g

Q19 idk whyyy

That helped,thanks for the effort

 

[Zepudee]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q21 (C)???
Q23 (B)???

Q21 The functional groups that react with Na are CO2H and OH, so three of any of these should be present in the compound. B and D are ruled out. NaOH will react with CO2H, so there should be 1 CO2H and 2 OH groups.

 

[SIstudy]

Q21 The functional groups that react with Na are CO2H and OH, so three of any of these should be present in the compound. B and D are ruled out. NaOH will react with CO2H, so there should be 1 CO2H and 2 OH groups.

thanks, but i'm still confused :/
I get D is ruled out butt how C I still umm :S :/

 

[ZaqZainab]

thanks, but i'm still confused :/
I get D is ruled out butt how C I still umm :S :/

Na can react with both -CO2H and OH,
there are 3 groups in C so -3 but NaOH only with -CO2H so -1
look at the charges

 

[SIstudy]

Na can react with both -CO2H and OH,
there are 3 groups in C so -3 but NaOH only with -CO2H so -1
look at the charges

okay got a bit, but the part where yu said "but NaOH only with -CO2H so -1"
tht I didn't get :/

 

[Snowysangel]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s13_qp_12.pdf 11: Answet is B

 

[sweet.sugar]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q28(C)
Q29-(D) explain plzz

 

[ZaqZainab]

okay got a bit, but the part where yu said "but NaOH only with -CO2H so -1"
tht I didn't get :/

Na will react with both Na and COOH okay so
when it reacts with 1 OH it will give charge of -1 and then another OH it will become -2 and then with COOH it will be -3 as the question says
and NaOH will only react with COOH
so it will give -1 with one COOH thats it
but for A there are 3 OH groups and 1 COOH

 

[Browny]

Please help!!!!

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
Q28(C)
Q29-(D) explain plzz

Hydrolysis of the ester will give an carboxylic acid and alcohol
here the acid will be CH3CH2CH2CO2H
and alcohol will be CH3OH
Molecular formula for acid C4H8O2 and so the empirical C2H4O