Chemistry: Post your doubts here!

[Youssef Tawil]

There has to be a attachment to 2 ADJACENT carbons which is C

 

[Snowysangel]

View attachment 45117
full explanation plx..step by step

C

 

[ashcull14]

ex

D

can u explain all the 3 ques plx

 

[Suchal Riaz]

who i n helll will think to do this correct only 1 mark omg jesus christ the merciful

it takes no more than 1 minute. and you have 1.5 minutes to do each question.

 

[Suchal Riaz]

why isn't the number of moles of H2 taken into account? why only N2? :/ :S

you could do that with H2 too.
number of moles of H2 used : number of moles of NH3 = 3:2
so (60 000 - 48 000):x=3:2
X=12 000*2/3=8000 moles = 136 Kg

 

[_Ahmad]

Need helpView attachment 45119

2 NaHCO3 + H2SO4 → 2 CO2(g) + 2H2O(l) + Na2SO4

n(H2SO4)=(7.15*10^-3)*0.1=0.715*10^-3 mol

using mole ratio n(NaHCO3)=2*n(H2SO4)=2*(0.715*10^-3)=1.43*10^-3 mol

since you have got n(NaHCO3) you can find mass of NaHCO3 reacted = n*(mr of NaHCO3)=0.1202g

%by mass of NaHCO3 =(0.1202/1)*100=12.012~12.0%

therefore answer =C

 

[SIstudy]

you could do that with H2 too.
number of moles of H2 used : number of moles of NH3 = 3:2
so (60 000 - 48 000):x=3:2
X=12 000*2/3=8000 moles = 136 Kg

oh okaayy thanks a lot
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q23 ?? :/ (ANS - B)
I don't really get the compound C drawn :S
can yu also help me with this, since no one is answerin :/

 

[_Ahmad]

Suchal Riaz

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

9(D),36(D),39(C)

 

[SIstudy]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D)
Q26 (B)
Q9 (D)
Q29 (D)
Q35 (B)
Q40 (A)

 

[Suchal Riaz]

oh okaayy thanks a lot
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Q23 ?? :/ (ANS - B)
I don't really get the compound C drawn :S
can yu also help me with this, since no one is answerin :/

As the compounds reacts with itself to form the compound shown it must have both -OH and -COOH groups.
if we break up the compound we get one single product.

 

[..sacrifice4Revenge..]

View attachment 45118

Its the old rule of electrochem, the one in O levels.
Remember the order, K,Na,Ca,Mg,Al,Zn,Fe,Pb,i dnt remember,Cu,
So Cu is more electro positive than Al and will be reduced at cathode, and vice versa

 

[Suchal Riaz]

Suchal Riaz

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

9(D),36(D),39(C)

question 9: the number of moles of solute increase on the right hand side so osmotic pressure increase
as glucose and fructose have different structural formula they are structural isomers.

 

[Rockstar RK]

Q4) Some bond energy values are listed below.
bond bond energy / kJ mol–1
C–H 410
C–Cl 340
Cl–Cl 244
Br–Br 193
These bond energy values relate to the following four reactions.
P Br2 → 2Br
Q 2Cl → Cl2
R CH3 + Cl → CH3Cl
S CH4 → CH3 + H
What is the order of enthalpy changes of these reactions from most negative to most positive?
A P → Q → R → S
B Q → R → S → P
C R → Q → P → S
D S → P → Q → R

 

[..sacrifice4Revenge..]

View attachment 45117
full explanation plx..step by step

+1 to this,
Ans is C

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D)
Q26 (B)
Q9 (D)
Q29 (D)
Q35 (B)
Q40 (A)

can you just say what is confusing you in each question to make it easy for us to answer?

 

[..sacrifice4Revenge..]

Q4) Some bond energy values are listed below.
bond bond energy / kJ mol–1
C–H 410
C–Cl 340
Cl–Cl 244
Br–Br 193
These bond energy values relate to the following four reactions.
P Br2 → 2Br
Q 2Cl → Cl2
R CH3 + Cl → CH3Cl
S CH4 → CH3 + H
What is the order of enthalpy changes of these reactions from most negative to most positive?
A P → Q → R → S
B Q → R → S → P
C R → Q → P → S
D S → P → Q → R

P is endo, so 193
Q Is exo, -244
R exo, -340
S endo, 410

Ans is c

 

[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
Q8 (D) [ i guess all these answers correctly, but i dont understand why ]

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

 

[Suchal Riaz]

Q4) Some bond energy values are listed below.
bond bond energy / kJ mol–1
C–H 410
C–Cl 340
Cl–Cl 244
Br–Br 193
These bond energy values relate to the following four reactions.
P Br2 → 2Br
Q 2Cl → Cl2
R CH3 + Cl → CH3Cl
S CH4 → CH3 + H
What is the order of enthalpy changes of these reactions from most negative to most positive?
A P → Q → R → S
B Q → R → S → P
C R → Q → P → S
D S → P → Q → R

calculate energy needed to break the bonds - energy released when bonds formed . the most negative asnwer on the right side and most positive to the left side. example:
in P: Br-Br is brocken and no bond is made so 193-0=+193
in Q: no bonds are broken only bond make is Cl-Cl so 0-244=- 244
in R CH3 + cl → CH3Cl only bond made is C-Cl. so -340
in S only bond broken is C-H = +410
negtive →→→ postive
-340(R) → -244(Q) → +193 → 410(S)

 

[_Ahmad]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf
Q37 (D)
Q26 (B)
Q9 (D)
Q29 (D)
Q35 (B)
Q40 (A)

just try copying and pasting the question or link with question number at the end on google
maybe you get some questions answered previously by the members. Because the questions you are asking might be repeating.

 

[..sacrifice4Revenge..]

calculate energy needed to break the bonds - energy released when bonds formed . the most negative asnwer on the right side and most positive to the left side. example:
in P: Br-Br is brocken and no bond is made so 193-0=+193
in Q: no bonds are broken only bond make is Cl-Cl so 0-244=- 244
in R CH3 + cl → CH3Cl only bond made is C-Cl. so -340
in S only bond broken is C-H = +410
negtive →→→ postive
-340(R) → -244(Q) → +193 → 410(S)

Bro dont waste your time on already answered questions