Chemistry: Post your doubts here!

[Casablanca]

20 What is the number of isomers of C2H2Cl2 including cis-trans isomers?
A 2 B 3 C 4 D 5
and B. besides cis trans whats the other isomer that we get?

I THINK the answer is 2.

Because number of isomers = 2^n and n is the number of double bonds. In the case of C2H2Cl2 we only have one double bond, so 2^1 is 2.

But I think you should wait for someone to confirm it, because I'm not that good at chemistry.

 

[smartangel]

I THINK the answer is 2.

Because number of isomers = 2^n and n is the number of double bonds. In the case of C2H2Cl2 we only have one double bond, so 2^1 is 2.

But I think you should wait for someone to confirm it, because I'm not that good at chemistry.

i chked the marking scheme it says C.

 

[smartangel]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_qp_1.pdf
Q3..please explain it to me!
also q12..shouldnt the answer be D?

 

[smartangel]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
in 5 why cant the answer be D? i dont get what the examiner report is trying to say. please explain!!!

 

[egy]

hi i just wanted to ask is any of u guys is from Egypt and appearing as a private candidate please reply

pleassssssssseeeeeeeeeeeeeeeeeee

 

[egy]

private student in Egypt

 

[smartangel]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Q34..plz explain second n third statements.
Q23 as well!

 

[egy]

no one is from egypt

 

[umarashraf]

they react to give salt and ALCOHOL in case of esters...so over here u get a sodium salt (i.e ethyl ethanoate )and an alcohol(ethanol)

what point you are actually trying to raise here...??? esters are hydrolysed first.. then the reaction is followed by mere titration... this is what i believe...

 

[1357913579]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_qp_1.pdf
Q3..please explain it to me!
also q12..shouldnt the answer be D?

number3 outer energy level should hhave one electron which is the case in B
number-12 i think thats the correct answer.
pi bond is formed by sideways overlap of p orbital in partD its i think diagonal sort of overlap whereas in partB its side ways overlap i suppose you would be confused by seing in part-B that its s orbital but no its p orbital bcause see clearly nucleus is in the middle of two circles so its lobe shaped which is p orbital
hope it helps

 

[gary221]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Q34..plz explain second n third statements.
Q23 as well!

For 23, thr will be 9 products formed, including Br2, ethane, n HBr...
the other 6 will be like CH3CH2Br, CH3CHBr2, CH3CBr3....n so on..
Hope i helped!!

i chked the marking scheme it says C.

r u sure the ms said C?? which ppr, nywy??

 

[Zsiddiqui]

ya deffa
http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s06_qp_1.pdf
Q no 10

my ans is A wbt u?

but d marking scheme ans IS C

2NO = (2/3)^2
N2O4 = (1/3)
Kp = (2/3)^2/(1/3)
= 4/3

 

[Zsiddiqui]

More doubts x_x . The correct answers are circled.

 

[hmlahori]

in 16 read the question again. it says the cell is kept cold. with cold Naoh NaClO is formed not NaClO3. you"ve to learn these rxns.
in 36, nitrogen dioxide is very much polar. positive nitrogen atom and 2 negative oxygen hence overall is it polar!

yes actually i know those reactions but i never really considered them to be involved here!
And i was just coming around to understanding how NO2 is polar because of the difference in electronegativities.
Well thanks a lot!

 

[1357913579]

in 16 read the question again. it says the cell is kept cold. with cold Naoh NaClO is formed not NaClO3. you"ve to learn these rxns.
in 36, nitrogen dioxide is very much polar. positive nitrogen atom and 2 negative oxygen hence overall is it polar!

please can you explain how no for basic hydride.
thanks

 

[saudha]

Use of the Data Booklet is relevant to this question.
What could be the proton number of an element that has three unpaired electrons in each of its
atoms?
A 5 B 13 C 15 D 21
why C.... why not B

 

[Inert.Phantom]

its simple....

do the electronic configuration

1s will hav 2e-
2s will have 2e-
2p will have 6e-
3s will have 2e-
3p wil hve 3e- .............. try it

 

[Inert.Phantom]

5 Given the following enthalpy changes,
I2(g) + 3Cl2(g) → 2ICl3(s) ∆H = –214kJmol
I2(s) → I2(g) ∆H = +38kJmol

What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)?
A +176kJmol
B –88kJmol
C –176kJmol
D –214kJmol

 

[Inert.Phantom]

2.920 g of a Group II metal, X, reacts with an excess of chlorine to form 5.287 g of a compound
with formula XCl2.
What is metal X?
A barium
B calcium
C magnesium
D strontium

 

[saudha]

2.920 g of a Group II metal, X, reacts with an excess of chlorine to form 5.287 g of a compound
with formula XCl2.
What is metal X?
A barium
B calcium
C magnesium
D strontium

the formula XCL2 shows i mole of X's mass will cover 2 of Cl ....so see the RMM of any of the options whose mass is close to 2*Cl
Cl-35.5X2=71
Ba-137...so nt possible
Ca-40....agn nt possible
Mg-24....does not = to 71
Sr-88....closest to 71...so D
u can also do the mole ratio: Mass/RMM