Chemistry: Post your doubts here!

[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!!!

 

[gary221]

y dos the bond length increase btween hydrogen chloride,hydrogen bromide and hydrogen iodide?

Cl is more reactive as compared to Br... so it forms a stronger bond, n as a result, bond length is shorter.
Same applies to Br as compared to I.

 

[smartangel]

21 What is the total number of different chloroethanes, formula C2H6-nCln, where n can be any
integer from 1 to 4?
A 4 B 6 C 7 D 8
ans C. how?

 

[smartangel]

30 Which pair of compounds is formed when the ester C2H5CO2CH3 is boiled with aqueous sodium
hydroxide?
A C2H5CO2H CH3OH
B C2H5CO2Na CH3ONa
C C2H5CO2Na CH3OH
D C2H5OH CH3CO2Na
ans C. why cant it be A or B? please explain my questions. i really need help!

 

[leosco1995]

30 Which pair of compounds is formed when the ester C2H5CO2CH3 is boiled with aqueous sodium
hydroxide?
A C2H5CO2H CH3OH
B C2H5CO2Na CH3ONa
C C2H5CO2Na CH3OH
D C2H5OH CH3CO2Na
ans C. why cant it be A or B? please explain my questions. i really need help!

Split the ester by drawing a straight line through the middle of O2 and you will get these 2 compounds:

C2H5C & CH3

The carbon without the hydrogen (first one) will be the acid and the other one will be the alcohol. So your alcohol is CH3OH and the acid is C2H5CO2H. Since you boiled with aq. NaOH, the carboxylic acid becomes C2H5CO2Na.

 

[umarashraf]

30 Which pair of compounds is formed when the ester C2H5CO2CH3 is boiled with aqueous sodium
hydroxide?
A C2H5CO2H CH3OH
B C2H5CO2Na CH3ONa
C C2H5CO2Na CH3OH
D C2H5OH CH3CO2Na
ans C. why cant it be A or B? please explain my questions. i really need help!

mate first of all .. alcohols donot react with sodium hydroxide... secondly propanoic acid is an acid while sodium hydroxide is a base... this will readily react and form salt + h2O.... (acid base titration)

 

[smartangel]

mate first of all .. alcohols donot react with sodium hydroxide... secondly propanoic acid is an acid while sodium hydroxide is a base... this will readily react and form salt + h2O.... (acid base titration)

thanks..plz answer this on too
21 What is the total number of different chloroethanes, formula C2H6-nCln, where n can be any
integer from 1 to 4?
A 4 B 6 C 7 D 8
ans C. how?

 

[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!!!

 

[umarashraf]

thanks..plz answer this on too
21 What is the total number of different chloroethanes, formula C2H6-nCln, where n can be any
integer from 1 to 4?
A 4 B 6 C 7 D 8
ans C. how?

yes.. the answer is C but due to lack of skills i cant draw all the structures here..but can guide you just by sayin k if you use 1 cl, you can only have 1 orientation .. by using 2,3orb 4 carbons you can only make 2 2 and 2 orientations of the structure of chloroethane...

 

[smartangel]

yes.. the answer is C but due to lack of skills i cant draw all the structures here..but can guide you just by sayin k if you use 1 cl, you can only have 1 orientation .. by using 2,3orb 4 carbons you can only make 2 2 and 2 orientations of the structure of chloroethane...

can you draw them on paint and then post it as a file? its ok. i"ll excuse the bad drawing if thats the problem

 

[hmlahori]

Have some doubts people give a response im posting this for the second time!

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_ms_11.pdf
Q16 I'm confused between options B & C. Clarify why its B.
Q36 The non-metallic element has to be nitrogen. It satisfies all the conditions in the question and the statements 1 & 2. But how is nitrogen dioxide polar?

 

[umarashraf]

can you draw them on paint and then post it as a file? its ok. i"ll excuse the bad drawing if thats the problem

mate i have my Maths P1 tomorrow...(Cambridge) so i hope you understand... drawing take a massive time for me on paint

 

[Oliveme]

Please help me with these questions 8, 11, and 17. http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w02_qp_1.pdf

And also, questions 16, and 26. http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s03_qp_1.pdf

 

[hihi]

thanks but can you explain why is this the answer?

u r wecome, it is correctly balanced equation and they ask u 4 which you put in front of (as far as i remember the question) I2 and H2O, u understand now?

 

[smartangel]

Have some doubts people give a response im posting this for the second time!

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_ms_11.pdf
Q16 I'm confused between options B & C. Clarify why its B.
Q36 The non-metallic element has to be nitrogen. It satisfies all the conditions in the question and the statements 1 & 2. But how is nitrogen dioxide polar?

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!

 

[smartangel]

mate i have my Maths P1 tomorrow...(Cambridge) so i hope you understand... drawing take a massive time for me on paint

oh its okay. thanks for the help though

 

[umarashraf]

oh its okay. thanks for the help though

you welcome mate.... will answer u tomorrow...!!!

 

[sumaiyarox:)]

Split the ester by drawing a straight line through the middle of O2 and you will get these 2 compounds:

C2H5C & CH3

The carbon without the hydrogen (first one) will be the acid and the other one will be the alcohol. So your alcohol is CH3OH and the acid is C2H5CO2H. Since you boiled with aq. NaOH, the carboxylic acid becomes C2H5CO2Na.

mate first of all .. alcohols donot react with sodium hydroxide... secondly propanoic acid is an acid while sodium hydroxide is a base... this will readily react and form salt + h2O.... (acid base titration)

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)

 

[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]

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?