Chemistry: Post your doubts here!

[pratikdahal]

Can anyone please help me out with this?? November 2008, Paper 4, Question 2(b).

 

[ousamah112]

Can anyone please help me out with this?? November 2008, Paper 4, Question 2(b).
View attachment 7680

only those reactants will take part in the slowest step if their order of reaction is other thn zero order. For step 1 slowest, no H+ takes part in reaction so its zero order and other two are first order. For step 2 to be slowest, all will be 1st order because HOI is proportional to the conc of H+ and IO- and IO- is proportional to H2O2 and I-. For third ans will be 1 2 2,for this look at all three equations.

 

[JD REBORN]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf
Q33 why is statement 2 incorrect?
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
In Q5 why isnt answer D?
In Q32 why is statement 1 correct and 2 and 3 wrong?
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_1.pdf
Q9,32
Plz anyone just explain them properly.Surely that cant be too hard??

 

[Zishi]

Could anyone explain what standard cell potential is?

Read any good textbook. . .

 

[étudiante]

Could anyone explain what standard cell potential is?

It is the potential difference measured when a metal in a solution of its ions is connected to a standard hydrogen cell.

 

[JD REBORN]

Q33 the statement IS correct but is not applicable to the situation as it has no bearing on the fact that hydrazine does not undergo spontaneous coombustion.

Q5 it should have only two lobes and not four

Q32
1) is correct because a substance will readily change to its more stable state (and this is implied in the question so this is the information you can dduce from the question)
2) The reactivity of carbon monoxide has nothing to do with enthalpy change of formation of the two substances, if it were combustion, then it would be relevant.
3) This is no doubt true, but the statement is reffering to a complete conversion and not equillibrium so you can ignore this.

The statements can be true but you need to choose the one RELEVANT to the question.

U have mixed up the questions.And judging by your response obviously are trying to prove the statements are wrong but they are correct 2 and 3.

 

[étudiante]

U have mixed up the questions.And judging by your response obviously are trying to prove the statements are wrong but they are correct 2 and 3.

can u rewrite dem again pls so dat i get which questions ur talking abt den?
i never said any of the statements are wrong... just irrelevant

 

[hm12]

Calculate the pH of the buffer formed when 10.0 cm3 of 0.100 mol dm–3 NaOH is added to 10.0 cm3 of 0.250 mol dm–3 CH3CO2H, whose pKa = 4.76.

please explain how the answer is 4.58?

 

[hassam]

well.....there are 0.001 moles of naoh and .0025 moles of acid.
now naoh will react with acid and the resulting solution contains .001 mole salt and .0015 mole unreacted acid.now finnd their conc with the total volume now being 20cm^3 and now simply apply the henderson-hasselbalch equation

 

[hassam]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_41.pdf
q 3 b (ii)
i cnt undrstnd ms.....smbody explain please

 

[Scafalon40]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdf
Q33 why is statement 2 incorrect?
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
In Q5 why isnt answer D?
In Q32 why is statement 1 correct and 2 and 3 wrong?
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_1.pdf
Q9,32
Plz anyone just explain them properly.Surely that cant be too hard??

Fellows need help with these paper 1 questions​

others have explained some of them but im not entirely satisfied.​

​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

http://www.xtremepapers.com/papers/...and AS Level/Chemistry (9701)/9701_w08_er.pdf​

Q3 how do we work out the answer of this question?(which is D)​

Q31 Why is the answer not A?​

Q38 Why is the answer not B?(someone in a previous post said that flourine has to be present in order for a hydrocarbon to be a flame retardant. Can someone confirm that and tell me why?)​

​

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf​

Q9 Why is the answer not A?​

Q31 Why cant the answer be B? The second statement seems correct.​

Lets make a deal...
I'll try to help you in your problems if YOU JUST ANSWER MY QUESTIONS!

 

[étudiante]

Lets make a deal...
I'll try to help you in your problems if YOU JUST ANSWER MY QUESTIONS!

what questions? i can try to help u...

 

[Scafalon40]

what questions? i can try to help u...

In my signature below

 

[gary221]

11 In which change would only van der Waals’ forces have to be overcome?
A evaporation of ethanol C2H5OH(l) → C2H5OH(g)
B melting of ice H2O(s) → H2O(l)
C melting of solid carbon dioxide CO2(s) → CO2(l)
D solidification of butane C4H10(l) → C4H10(s)
Ans C
Why is it not D?
Butane is also non polar, in addition to CO2

it cant be D bcoz they r tlkng abt solidification of butane, in which van der waals' forces dnt hv 2 b ovrcum

 

[gary221]

Fellows need help with these paper 1 questions​

others have explained some of them but im not entirely satisfied.​

​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

http://www.xtremepapers.com/papers/...and AS Level/Chemistry (9701)/9701_w08_er.pdf​

Q3 how do we work out the answer of this question?(which is D)​

Q31 Why is the answer not A?​

Q38 Why is the answer not B?(someone in a previous post said that flourine has to be present in order for a hydrocarbon to be a flame retardant. Can someone confirm that and tell me why?)​

​

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf​

Q9 Why is the answer not A?​

Q31 Why cant the answer be B? The second statement seems correct.​

For 3, v hv 2 see which pair of atoms hv 1 electron in thr s orbital...
In A, the electronic configuration of Ca is [Ar], 4S2...ie 2 electrons in s orbital thus A is wrong
In B, the e.c. of Cu is [Ar], 3d10, 4S1...bt Be is 1S2, 2S2.....thus B is wrong.
In C, the e.c. of H is 1S1...bt He is 1S2...thus C is wrong.
In D, Li = 1S2, 2S1...n Cr = [Ar], 3d5, 4S1....so D is correct

 

[étudiante]

11 In which change would only van der Waals’ forces have to be overcome?
A evaporation of ethanol C2H5OH(l) → C2H5OH(g)
B melting of ice H2O(s) → H2O(l)
C melting of solid carbon dioxide CO2(s) → CO2(l)
D solidification of butane C4H10(l) → C4H10(s)
Ans C
Why is it not D?
Butane is also non polar, in addition to CO2

it says OVERCOME.... in solidifiction, they will be made stronger... dats y its not the answer...
only in C will they be broken, for the others threr are H-bonds as well...

 

[gary221]

For 38, D is the only ans bcoz
Halogenoalkanes in which all the hydrogen atoms in the alkane have been replaced by halogen atoms are difficult to burn, thus used as fire retardants...

 

[hm12]

Fellows need help with these paper 1 questions​

others have explained some of them but im not entirely satisfied.​

​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

http://www.xtremepapers.com/papers/...and AS Level/Chemistry (9701)/9701_w08_er.pdf​

Q3 how do we work out the answer of this question?(which is D)​

Q31 Why is the answer not A?​

Q38 Why is the answer not B?(someone in a previous post said that flourine has to be present in order for a hydrocarbon to be a flame retardant. Can someone confirm that and tell me why?)​

​

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf​

Q9 Why is the answer not A?​

Q31 Why cant the answer be B? The second statement seems correct.​

for the first paper i.e 08 Q3 electronic configuration of Li is 1 S^2 and 2 S^1 and for Cr it is 1S^2, 2S^2, 2P^6,3S^2,3P^6,3D^5 and 4 S^1 so means both Li and Cr have one electron is their S orbital so answer is D for Q31 its not A because permanent dipole occurs in molecules or compounds which have a difference of electronegativity and for Q38 read the following link http://www.chemguide.co.uk/CIE/section103/learningcd.html

 

[gary221]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf​

Q9 Why is the answer not A?​

Q31 Why cant the answer be B? The second statement seems correct.​

For 9, the ans is nt A, bcoz the total mass has to be taken ie mass of HCl + mass of NaOH which = 100 cm3
then delta H =(mass *specific heat capacity * temp change)/no. of moles
so the ans is C

 

[hmlahori]

for the first paper i.e 08 Q3 electronic configuration of Li is 1 S^2 and 2 S^1 and for Cr it is 1S^2, 2S^2, 2P^6,3S^2,3P^6,3D^5 and 4 S^1 so means both Li and Cr have one electron is their S orbital so answer is D for Q31 its not A because permanent dipole occurs in molecules or compounds which have a difference of electronegativity and for Q38 read the following link
http://www.chemguide.co.uk/CIE/section103/learningcd.html

For 3, v hv 2 see which pair of atoms hv 1 electron in thr s orbital...
In A, the electronic configuration of Ca is [Ar], 4S2...ie 2 electrons in s orbital thus A is wrong
In B, the e.c. of Cu is [Ar], 3d10, 4S1...bt Be is 1S2, 2S2.....thus B is wrong.
In C, the e.c. of H is 1S1...bt He is 1S2...thus C is wrong.
In D, Li = 1S2, 2S1...n Cr = [Ar], 3d5, 4S1....so D is correct

Isnt the electronic configuration of Cr = 1s2 2s2 2p6 3s2 3p6 4s2 3d4?
Doesnt the 3d orbital contain 10 electrons and come after the 4s orbital as it has a higher energy?