• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Chemistry: Post your doubts here!

Messages
887
Reaction score
466
Points
73
for Q40 primary or secondary alcohol oxidize to form aldehyde and ketone respectively. u reverse the process that is called reduction
 
Messages
887
Reaction score
466
Points
73
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
Do you know how to do Qs 33 , 32, 20, 16, 11 in 01/M/J/2003?
I am a bit confused about the answers to those Qs.
for Q11
lone pairs make compounds polar more lone pairs means more polar so ammonia can not be more polar than water.
stronger base will pull those H+ protons with greater ease.
for Q16
for option A u get a complex ion where Cl has oxidation number of -1
for option B u get HCl again -1
for option C u get NaClO here u get +1
for option D u get NaClO3 here u get +5 so this is the correct answer.
for q32
right hand side of the molecule is polar as the oxygen atom has lone pairs any compound that has lone pair is considered polar.
like gets like which means polar molecule dissolves in polar and non polar dissolves in nonpolar. so polar cant dissolve in non polar oil u know oil does not dissolve in water.
for q33
refer to this diagram
when u break the bonds in graphite and diamond u get carbon gas carbon gas would be at the same energy that is the hess law.

Diamond and graphite.jpg
 
Messages
2,824
Reaction score
3,730
Points
273

For question 11, I also had a doubt...
Q21--> A compound will not have cis trans isomers in one case, which is when 2 identical groups are present on the same carbon atom, so instead of R here u shd have CH2CH3 which is the same as C2H5 in D :)
For question 29, I guess this comes from ur knowledge (I mean just memorisation of the reactions and their conditions) :)
h4rriet Can u please check out question number 11 ? :D
 
Messages
93
Reaction score
13
Points
18
for Q11
lone pairs make compounds polar more lone pairs means more polar so ammonia can not be more polar than water.
stronger base will pull those H+ protons with greater ease.
for Q16
for option A u get a complex ion where Cl has oxidation number of -1
for option B u get HCl again -1
for option C u get NaClO here u get +1
for option D u get NaClO3 here u get +5 so this is the correct answer.
for q32
right hand side of the molecule is polar as the oxygen atom has lone pairs any compound that has lone pair is considered polar.
like gets like which means polar molecule dissolves in polar and non polar dissolves in nonpolar. so polar cant dissolve in non polar oil u know oil does not dissolve in water.
for q33
refer to this diagram
when u break the bonds in graphite and diamond u get carbon gas carbon gas would be at the same energy that is the hess law.

View attachment 28218

Thanks.
Your explanations were very helpful.
 
Messages
189
Reaction score
118
Points
28
sorry if i am annoying you !
y not a ketone .... how u knew it gonna be an acid
because when the double bond broke, the C was bonded to only one other C and one H and double bonded to an O which is a CHO group of aldehyde. Always just join an O atom whenever u break a double bond using KMnO4. then check if the C is bonded to 1 or 2 other C. If its bonded to 1 C then make an acid. If its with 2 other C then its a ketone :)
 
Messages
189
Reaction score
118
Points
28
For question 11, I also had a doubt...
Q21--> A compound will not have cis trans isomers in one case, which is when 2 identical groups are present on the same carbon atom, so instead of R here u shd have CH2CH3 which is the same as C2H5 in D :)
For question 29, I guess this comes from ur knowledge (I mean just memorisation of the reactions and their conditions) :)
h4rriet Can u please check out question number 11 ? :D
For Q11 - for A XYn-->X + nY
there are n X-Y bonds in the molecule. Enthalpy change is the energy needed to break these n bonds. They all break and form atoms of X and Y. So dividing the enthalpy by n we get the energy for one bond.
 
Messages
189
Reaction score
118
Points
28
The answer is C. Why cant the it be D?
there is no affect of the Cl-Cl bond or Br-Br bond here. The main bond here is H-Cl and H-Br. U should refer to there bonds to answer the question. Bond energies are diff according to the elements they are bonded to so we cant relate Cl-Cl and Br-Br to H-Cl and H-Br
 
Messages
2,703
Reaction score
3,939
Points
273
For Q11 - for A XYn-->X + nY
there are n X-Y bonds in the molecule. Enthalpy change is the energy needed to break these n bonds. They all break and form atoms of X and Y. So dividing the enthalpy by n we get the energy for one bond.
caan you explain again :/
 
Messages
325
Reaction score
215
Points
53
For question 11, I also had a doubt...
Q21--> A compound will not have cis trans isomers in one case, which is when 2 identical groups are present on the same carbon atom, so instead of R here u shd have CH2CH3 which is the same as C2H5 in D :)
For question 29, I guess this comes from ur knowledge (I mean just memorisation of the reactions and their conditions) :)
h4rriet Can u please check out question number 11 ? :D

11 is A, if I'm not mistaken. If you take n to be 4, for example, you'll see there are 4 X-Y bonds, so the total energy can be divided by 4 to get the energy for one bond. Not so for the B, C and D.
 
Messages
512
Reaction score
64
Points
38
11 is A, if I'm not mistaken. If you take n to be 4, for example, you'll see there are 4 X-Y bonds, so the total energy can be divided by 4 to get the energy for one bond. Not so for the B, C and D.



In A) it says XYn ..... but in D) it says nXY , so doesnt D) tell us that there are 'n' X-Y bonds.....
 
Top