Chemistry: Post your doubts here!

[syed1995]

i dont get this one

It's mass of Cl2... Meaning two Cl2 atoms are bonded...

It can either be Cl35 + Cl35 giving 70 mass.. or Cl35 + Cl37 .. giving 72 Mass .. or Cl37 + Cl37 giving 74 mass... hence 3 peaks.!

 

[1357913579]

That was the paper which you linked :\

soory bro i just realized it was my mistake
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w09_qp_11.pdf
of this paper can u please solve number-28
thanks alot

 

[1357913579]

another urgent doubt please help
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
number-38
i know tht 2 is correct but cant understant how 3 is correct as well?

 

[A star]

soory bro i just realized it was my mistake
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_11.pdf
of this paper can u please solve number-28
thanks alot

D?

 

[A star]

another urgent doubt please help
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
number-38
i know tht 2 is correct but cant understant how 3 is correct as well?

3 is correct as it will form a diester try making a diester and you will see that it will form the co,pound with the formulae

 

[1357913579]

D?

no bro answer is (C) please eplain

 

[A star]

no bro answer is (C) please eplain

sorry i drew a ketone look HCN addition reactions CN acts as a neuclophile juse use the anion generated in its place ans since its an aldehyde it must have the anion an Oh an H group and a alkyl chain and only C fits the bill (Y)

 

[A star]

i am getting a confidence boost by solving these questions and i need it for tuesday so yuppp i'm on FiiRREE!!

awesome keep it up yup u on fire all right

 

[1357913579]

3 is correct as it will form a diester try making a diester and you will see that it will form the co,pound with the formulae

can u please write as an equation or draw it. thanks alot

 

[A star]

it will form like this
H3COOC COOCH3 h ence check its molecular formulae it will be the same

 

[1357913579]

sorry i drew a ketone look HCN addition reactions CN acts as a neuclophile juse use the anion generated in its place ans since its an aldehyde it must have the anion an Oh an H group and a alkyl chain and only C fits the bill (Y)

so u mean to say first cn gets attached then it is replaced by -ch2c00ch3?

 

[1357913579]

it will form like this
H3COOC COOCH3 h ence check its molecular formulae it will be the same

oh yeah got it bro so we use 2 methanol

 

[A star]

so u mean to say first cn gets attached then it is replaced by -ch2c00ch3?

no the anion acts as a neuclophyl itself instead of CN as CN is not present there read the question

 

[A star]

oh yeah got it bro so we use 2 methanol

yup cause a diol forms diester

 

[1357913579]

no the anion acts as a neuclophyl itself instead of CN as CN is not present there read the question

so bro u mean to say first -ch2co2ch3 attaches towards the carbon in the aldehyde
then oxygen gets positive charge then the hydrogen released from the ch2c00ch3 attaches to the oxygen forming oh?
because thats what happens in the mechanism if only hcn would have reacted right?

 

[A star]

so bro u mean to say first -ch2co2ch3 attaches towards the carbon in the aldehyde
then oxygen gets positive charge then the hydrogen released from the ch2c00ch3 attaches to the oxygen forming oh?
because thats what happens in the mechanism if only hcn would have reacted right?

you got it (Y)

 

[cute97]

Q1's answer is C. from the data u can infer that 50 cm3 of O2 was used to burn 10cm3 of hydrocarbon (CxHy)
make up an equation for the unknown hydrocarbon for ur aid and u'll c that 1 mol of CxHy requires 5 moles of O2 to produce 3 mol of CO2. 6 O go into the CO2 and the remaining 4 (from 5 O2) go to the H2O which means that 4 H2O molecules were formed. so we have 8 H and 3 C thus the ansewr.

Q2's answer is bcz 2 mol of NaN3 make 3 mol of N2 which means 1 mol makes 1.5 mol of N2 directly. then the Na produced also makes N2.
wth 2 mol of NaN3 we get 2 mol of Na so with 1 mol we get 1 mol of Na.
10 mol of Na produce 1 mol of N2 so 1 mol produces 0.1 mol
so total N2 produced is 1.5 + 0.6 = 1.6mol

i don't get q10 so if u get an answer for that tag me ^_^

Thank you yhh i got an answer for Q10 may-june-06

Kp= p2NO2/pN2O2
There are three molecules, 1 on left and 2 on right. So the pressure is shared by 3 molecules. The pressure on left should be 1/3 and on right 2/3. Using these pressure in the Kp equation:
2/3 ^2 / 1/3
We get answer of 4/3 which is (C).

 

[Student12]

HEEEEELLLLLLLLLLLLLLLLLLLLLLLLP !

A few questions i'm not able to solve on Moles..
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w02_qp_1.pdf Q1 (C)http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w05_qp_1.pdf Q1(C)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf Q1,Q2,Q4
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf Q2
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s05_qp_1.pdf Q2(why is it not 1.5?)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdf Q2

Could someone pls. explain these answers in detail? Someone had helped but not so clear yet.

 

[strangerss]

Thankss but i never saw such a working i think my teacher missed explaining or wat

If your teacher made you understand in a different way ,then it doesn't matter I guess right!

 

[darkxangel]

umm i think an aldehyde will be formed bcz it is distilled (and not refluxed) so write out an eqation for the formation of an aldehyde from this alcohol.
calculate the moles of ethanol according to the mass given and then use mole ratio (as in the equation) to find moles of aldehyde. use moles and Mr of aldehyde to find mass. use the percentage yield formula and incorporate the theoretical yield and the percentage yield in it to find the practical - or actual - yield of the product i.e. aldehyde.
if u cant solve it then tell me and i'll do it. i don't have a pen and paper handy ryt now

Thanks I got it !