Chemistry: Post your doubts here!

[A star]

thanks

4c) as higher the temprature further the curve meaning Q and catalysed reaction has lowered Ea
5d) as only electron shielding effect is able to reduce ionisation energies sig and all the atoms have valance e in s shell and inc in neuclear charge will inc ionistion energy while group 1 elements have only one valnce e

 

[A star]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_11.pdf
please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance

10is c as only graphite T conducts electricity in solid state and MgO has higher boiling point than NaCl as stronger bonds
11c) as in a and b hydrogen bond needs to also be broken and in d well is endothermic hence c
14d) as its a prroperty

 

[A star]

guys, does anyone know how the marks are calculated for AS levels to get a mark out of 130?

well for AS level its around this 50-60 for p2 27 for p1 and the remaining for p3

 

[snowbrood]

its just one question
q1 molar enthalpy change of the reaction of pure sodium carbonate with hydrochloric acid is 49.5KJmol^-1
2.6g of washing soda was added to 50cm^3 of dilute hydrochloric acid in a plastic cup the temperature rose by 5C(specific heat capacity of the resulting solution=4.3) calculate the molar enthalpy change for the reaction of washing soda with dilute hcl
answer -43.8kjmol^-1
scourserlfc,

 

[Alice123]

please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

 

[snowbrood]

please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

question no 4
bond breaking is endothermic which has a positive enthalpy change
bond forming is exothermic which has negative enthalpy change
R and Q is bond forming as u can see
p and s is bond breaking the magnitude of bond energy is given u can now find out which reaction is more negative
for question 7
u might know that a catalyst increases the rate of reaction of both endothermic and exothermic so does temperature .
the equilibrium is going to shift to backward reaction but that is not what the question demands. increasing temperature will increase the rate of exothermic and endothermic .
for question 10
ph closer to 7 means weak acid or weak alkali
student p makes a false statement maybe he was drunk . what is a difference between a strong alkali strong acid and a weak alkali weak acid .
strong acid or alkali is what that dissociates or ionizes completely . dissociation or ionization is the same thing here.

for question 14
astatine and iodide ion are insoluble in both aqueous and concentrated ammonia
bromide ion is soluble in concentrated ammonia but insoluble in dilute ammonia
chlorine is soluble in dilute ammonia

 

[snowbrood]

please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

 

[snowbrood]

Alice123

 

[scouserlfc]

Please any1 solve this: oct/nov 2011/22 Q4 (a)http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_22.pdf

top left box
CH3CH2OHCH3
top right box
CH3CH2COOH the other product is inorganic and is CO2

V= CH3CH2CHOHCH2OH

W= CH3CH2COCHO

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_11.pdf
please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance

4 =C because the curve (Boltzman) becomes more flatter and moves towards the right a little (increasing the molecular speeds while at the same time increasing the molecules with activation energy ! for the catalysed reaction just remember its definition that it provides an alternative route for the reaction,which has a lower activation energy !

5=D none of those options happen except last one more the inner shells are present more the inner electrons repel the outer ones away from nucleus and hence nucleus has almost no control over the outer ones

in 7 yes the backward yield will increase but building high pressure chambers capable of resisting more than 1MPa of pressure is expensive and so a compromise between the equilibrium concentration and economical value of the reaction has to be achieved otherwise the reaction will be very uneconomical thats why answer is B

10=C because as we all know ions never conduct electricity in solid form and also that mp and bp of MgO is bound to be bigger than NaCl because of its smaller ionic radius and more charge on its ions,then the third one is graphite due to high mp and bp but also because of its electrical conductivity in solid form a property which SiO2 doesnt have

11=answer is C,because in A and B the effect of other forces except hydrogen bonding is very less and hence they are mostly overcome,in D you are actually solidifying so u are actually helping in formation of Van der walls,in C you have CO2 being melted breaking VDW forces,(it has these forces and not dipol-dipole because CO2 shape is linear cancelling out effect of each O atom )

14=D because X is MgO and it has Mr of 40.3,is a white solid and is basic metal oxides are basic mostly but the solubility of MgO is very less the Mg(OH)2 formed in water is sparingly soluble and solubility increasing down the group due to factors which we study in A2

 

[Alice123]

question no 4
bond breaking is endothermic which has a positive enthalpy change
bond forming is exothermic which has negative enthalpy change
R and Q is bond forming as u can see
p and s is bond breaking the magnitude of bond energy is given u can now find out which reaction is more negative
for question 7
u might know that a catalyst increases the rate of reaction of both endothermic and exothermic so does temperature .
the equilibrium is going to shift to backward reaction but that is not what the question demands. increasing temperature will increase the rate of exothermic and endothermic .
for question 10
ph closer to 7 means weak acid or weak alkali
student p makes a false statement maybe he was drunk . what is a difference between a strong alkali strong acid and a weak alkali weak acid .
strong acid or alkali is what that dissociates or ionizes completely . dissociation or ionization is the same thing here.

for question 14
astatine and iodide ion are insoluble in both aqueous and concentrated ammonia
bromide ion is soluble in concentrated ammonia but insoluble in dilute ammonia
chlorine is soluble in dilute ammonia

thanks and also explain no 21,

 

[sweetjinnah]

top left box
CH3CH2OHCH3
top right box
CH3CH2COOH the other product is inorganic and is CO2

V= CH3CH2CHOHCH2OH

W= CH3CH2COCHO

i wanted 2 know da explanation for V and W please?

 

[yubakkk]

i need help in this question
please give full detail answer with process.
why answer is doubled.

 

[yubakkk]

 

[yubakkk]

i need help in above question
please give full detail answer with process.
why answer is doubled.​

 

[Muhammad Bin Anis]

i need help in this question
please give full detail answer with process.
why answer is doubled.

i need help in above question ​

please give full detail answer with process.​

why answer is doubled.​

the answer is doubled because the equation says
"for decomposition of every 2 moles of NaHCO3,
1 mole of H2O and CO2
are produced.
so when you take Mr of one mole of H2O and CO2, you need to consider that there should have been 2 moles of NaHCO3

 

[Chaitanya Agrawal]

Hi everyone, AsSalamoAlaikum Wr Wb..

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah members around will help you.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!

Chemistry Notes:


http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Tips for solving chemistry MCQs 9701/01

Chemistry P5 Tips and Notes

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.


Regards,
XPC Staff.

how can we get october november 2012 papers?they arent on xtremepapers yet but are there any third party which have released them?

 

[Muhammad Bin Anis]

Anyone know how to do this please?
View attachment 21434
I know the answer has to be either A or C since it's trans, but I have no clue how to calculate the number of double bonds... I thought it would be two as there's a C=C double bond in a cyclohexene ring and the other is given in the question between Carbons 11 and 12 (aldehyde doesn't count as there's no C=C bond). So how would you arrive at a total of 5?

i remember this was explained by a user last year in detail
go through the previous posts
by the way, here i go
consider the general formula of an aliphatic alkane chain
its CnH2n+2 (where n denotes the number of C/H present in the molecule)
so when there 20 carbon atoms present, there should have been [(2x20)+2=42] hydrogen atoms present.
but the number of hydrogen atoms present here are 28
which means theres a difference of 12 hydrogen atoms
Including an Oxygen atom (as the compound is an aldehyde) means you lose out 2 hydrogen atoms
12-2= 10
the difference now remaining is 10
Recall the basics
whenever there is a double bond you lose out two hydrgen atoms
i.e one from each of the carbon atoms that make double bond
therefore dividing 10 by 2 gives you 5
which should be the number of carbon=carbon double bonds

 

[PhyZac]

Asslamu Alikum wa rahmatullahi wa barakatoho..

Can someone explain why the answer for 3 (a) (ii) is K (potassium)

 

[aseelz]

SALAAAAAAM PEOPLE
does anyone have question papers from june 2000 till 2002 + the marking schemes? i want paper 1, 2 and 3 plz if not possible only paper 1 if not possible only the marking schemes ..thnx

 

[littlecloud11]

Asslamu Alikum wa rahmatullahiView attachment 21507 wa barakatoho..

Can someone explain why the answer for 3 (a) (ii) is K (potassium)

Well, the general trend for the ionic radii is that it decreases as we move from left to right across the periodic table (owing to an increasing nuclear charge of the ions as we move towards the right). The greatest number of electronic shells in the ion is obviously present in elements of the third period compared to the other two and abiding by the aforementioned trend potassium would be the largest cation.