Chemistry: Post your doubts here!

[aaaamfa]

I need help regarding question no 11 in the following paper

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_13.pdf

Thanks for any explanation

 

[Browny]

For question-4,
Heat energy required to break the bonds-Heat energy released in forming the bonds=Enthalpy Change
496+994-2x=180
2x=1310
x=655

N to N bond is 944 not 994.

 

[doremon]

N to N bond is 944 not 994.

it is 994

 

[Snowysangel]

Hi there, please type the answers next to the questions to make it easier to reply.

Q23. Products formed CH3CH2OH, CH3CH2COONa
% of CH3CH2OH = Mr of CH3CH2OH/(Mr of CH3CH2O- + Mr of CH3CH2COONa) x 100% = 46/(46+96) x 100% = 32.3%

Q30.
Statement 2: True
PV=nRT
n/V=P/RT
density =P/RT
Therefore, density is inversely proportional to T

Statement 3: False
Temperature should be in Kelvins not degree Celsius

Q40. Conditions for nucleophilic substitution of halogen (on halogen alkane) with NH2, is to heat the halogenalkane with conc NH3 in sealed tube.

Oh thanks but I meant q31 and not q30 the answer is B

 

[doremon]

I need help regarding question no 11 in the following paper

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_13.pdf

Thanks for any explanation

the answer is C. it is very simple. The question says that the total mole is (2+x). expanding this would mean for P mole at equilibrium is (2-x) for R it is x which means mole for Q at equilibrium must be x ergo the answer is C.

 

[GCE As and a level]

Metanoia
To wat time r u available today ???
Wat is the time currently in ur country
THNX

 

[Snowysangel]

How does solid iodine contain more then one type of bonding? Why is there only one kind in silicon dioxide?

 

[doremon]

How does solid iodine contain more then one type of bonding? Why is there only one kind in silicon dioxide?

could you elaborate on what you mean by "bonding". Do you mean intermolecular forces or intramolecular forces?

 

[aaaamfa]

the answer is C. it is very simple. The question says that the total mole is (2+x). expanding this would mean for P mole at equilibrium is (2-x) for R it is x which means mole for Q at equilibrium must be x ergo the answer is C.

No but the ans is B

 

[UXm@N]

explain following

 

[doremon]

No but the ans is B

I am terribly sorry. Here is the correct explanation. Hope this helps

equilibrium: x moles of R, therefore there must be 2x moles of Q (as the ratio of Q to R is still 2:1). P will be 2-2x moles (we subtract Q from P this time because P is the same as Q in equilibrium in this equation)
Add them up: x + 2x + 2 - 2x = x + 2 so B is the correct answer

 

[Abdul Basit]

Question 20 please...

 

[Browny]

it is 994

I checked the syllabus Data booklet.

 

[Zepudee]

Hi, please include the answers to make it easier for us to reply.

w03qp1

Q3. C6H12 + 9O2 --> 6CO2 + 6H2O
moles of H2O : moles of CO2
6:6

mass of H2O absorbed : mass of CO2 absorbed
6 x 18: 6 x 44
0.41:1

Q27. Butanol has the following structural isomers
View attachment 45007

2-Butanol has a chiral carbon, so it has two optical isomers. Total 5 isomers

Q27. Both are primary alcohols, both can be oxidised.
The first one is resistant to dehydration but not the second one.

Q40. Substance 2 is a ionic compound (high boiling point) , it would be found left in the distilling flask and not the distillate.

Can you please explain further more for the Q27? Can you also please draw (CH3)3CCH2OH? I thought it is a tertiary alcohol? And why is it resistant to dehydration but not the second one? Sorry! But Thank you so so much! Next time I will include answers in it

 

[Zepudee]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf

Q3 (C), Q23 (D)

 

[doremon]

I checked the syllabus Data booklet.

check it again.

 

[GCE As and a level]

Metanoia , ZaqZainab , @ Every One , Could u Plz help me with this
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s05_qp_1.pdf

Q2..Answer B
Q13.Answer B>>>Why it is not Mg ??Mg is just beside Al , so i thought that it will have a similar Electronegativity as Mg.
Q15.Answer C>>>When H2SO4 acts as an acid and when it acts as an oxidizing agent?
Q31.Answer A>>>I know that this is simple, but i am always confused with this type,So is there any hint??
Q32.Answer D
Q33.Answer B
Q40.Answer B

THNX in advance

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s05_qp_1.pdf

Q19, how is it nucleophillic substitution, i mean Br is an electrophile.

 

[loveyuan]

How does solid iodine contain more then one type of bonding? Why is there only one kind in silicon dioxide?

I-I bond by covalent bond .
I2 molecule bond by van de waal

silicon dioxide only bond by covalent bond

 

[loveyuan]

Pentanol, C5H11OH, has four structural isomers that are primary alcohols.
How many of these primary alcohols contain a chiral carbon atom?
A0
B1
C2
D3

anyone ? thanks in advance