Chemistry: Post your doubts here!

[Casablanca]

Well the first answer shud be D (sodium bromide)
beacasue bromide ions are oxidised form Br- to Br2. (Oxidising power of halogens decreases down the group whereas reducing power increases


Cl2O7 is the most acidic . U have misinterpreted or probably theres some misconception

Thank you for the first one.

As for the second one, yes, you are right. I accidentally wrote that acidity decreases, whereas acidity actually increases, but since the graph goes down, I misinterpreted it.

So, yeah, I know Cl2O7 is most acidic, but is it a lot more acidic than SO3 and P4O10? As in, would the graph be at an incline, or straight?

 

[LimeReem]

Guys why is HF3 insoluble in water? please provide reasons! =)

 

[Muhammad Bin Anis]

Thank you for the first one.

As for the second one, yes, you are right. I accidentally wrote that acidity decreases, whereas acidity actually increases, but since the graph goes down, I misinterpreted it.

So, yeah, I know Cl2O7 is most acidic, but is it a lot more acidic than SO3 and P4O10? As in, would the graph be at an incline, or straight?

yup man , because chlorine goes for the highest oxidation (+7) , in Cl2O7. it makes the most acidic of all period three solutions

 

[mominzahid]

Oh, sorry I was wrong there, it does have a +2 charge. :\ Actually, all of the other elements are larger but beryllium is the only one which has the same charge density as Al. You can figure that out from the data booklet, that's why it said "use of the data booklet is relevant to this question".

all these elements belong to group 2. and why cant it be magnesium aluminium is right next to magnesium in periodic table?

 

[KurayamiKimmi]

Guys why is HF3 insoluble in water? please provide reasons! =)

are you sure its HF3 ?
i think you're confusing it with HF and in that case it is soluble

 

[mominzahid]

It is very helpfull. Thanks very much Are you doing AS Chemistry exam in May??

Yes.. sadly yess.. my chemistry sucks lol.. i cant get above 30 in MCQ paper i dont know what im gonna do lol...

 

[LimeReem]

are you sure its HF3 ?
i think you're confusing it with HF and in that case it is soluble

Yes its HF3 , it says its insoluble too.. friend asked me this question

 

[Student12]

The equation below represents the combination of gaseous atoms of non-metal X and of
hydrogen to form gaseous X2H6 molecules.
2X(g) + 6H(g) → X2H6(g) ΔH = –2775 kJ mol–1
The bond energy of an X–H bond is 395 kJ mol–1.

What is the bond energy of an X–X bond?
A – 405.0 kJ mol–1
B – 202.5 kJ mol–1
C +202.5 kJ mol–1
D +405.0 kJ mol–1

How is the answer D ?

 

[KurayamiKimmi]

I need help again
i need help with question no.2,12,16,18,26,and 36
please do try to explain the answers and thank you for any help ^_^
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s07_ms_1.pdf

 

[driggerbilal]

^awesome !thnx

 

[KurayamiKimmi]

Yes its HF3 , it says its insoluble too.. friend asked me this question

The only thing i can find by googling HF3 is headphones and missiles o_o
ask your friend again

lemme try searching again

 

[xxfarhaxx]

Q-6, 8, 9, 10, 18, 25, 35
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s10_ms_11.pdf

i believe its the 3rd time i'm posting :/

Q9 - find da mols of each compound usn mols= mass/molar mass
nd ues ths mols to find the vol... usng mols=vol/molar vol (molar vol=24dm)

A- mr of O2= 32
3.2/32= 0.1 mols
since mols=vol/molar vol
vol= mols*molar vol
0.1*24=2.4dm

B- mr of N2 = 28
5.6/28=0.2 mols
vol= 0.2*24= 4.8 dm

C- mr of SO2= 64
8/64= 0.125 mols
vol= 0.125*24= 3dm (the ans)

D- mr of CO2=44
11/44=0.25 mols
vol= 0.25*24=6 dm

Q10..student P says X is a strong acid..bt the pH given is 6, whch is almost neutral so student P is wrong..so da nly option without P is D which is d aans!!!

Q25- when an ester is hydrolysed it will gve its respective carboxlyic acid n alcohol..in ths cse C3H7OH wil b da alcohol n C2H4O2 will b da acid.. since da acid is nt gven as an option, B is da ans..

hpe i mde sumthn clear????

 

[hihi]

Yes.. sadly yess.. my chemistry sucks lol.. i cant get above 30 in MCQ paper i dont know what im gonna do lol...

me too, MC is very tricky and I cant get more than 30 too but still i am trying.. good luck for the exams!!!

 

[xxfarhaxx]

is MgO n Al2O3 insoluable in water???

 

[Student12]

In a car engine, non-metallic element X forms a pollutant oxide Y.
Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts
with ½ mol of gaseous oxygen.
What can X be?
1 carbon
2 nitrogen
3 sulfur

The answer is C 2 & 3 are right ??

 

[Casablanca]

is MgO n Al2O3 insoluable in water???

MgO is soluble. MgO(s) + H2O(l) -> Mg(OH)2(aq) (weakly alkaline solution)

Al2O3 does not react or dissolve in water. However, it reacts when added to acids or alkaline solutions. But still insoluble in water.

 

[hihi]

can some1 help me from these, please:
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_11.pdf
Q11, Q13,Q23,Q29

 

[samwickz]

10 At a total pressure of 1.0 atm, dinitrogen tetraoxide is 50% dissociated at a temperature of 60 oC, according to the following equation
N2O4 = > 2NO2

What is the value of the equilibrium constant, Kp, for this reaction at 60 oC?

A
1/3atm

B
2/3atm

C
4/3atm

D
2atm

helpppppppppppppppppppppppppppppppppppppppp the correct ans is C how 2 get it

 

[mominzahid]

me too, MC is very tricky and I cant get more than 30 too but still i am trying.. good luck for the exams!!!

To you too...
Im hoping if i nail the other exams and even if i get less marks in MCQ's it wont matter much.. but lets hope for the best.

 

[gary221]

is MgO n Al2O3 insoluable in water???

MgO is slightly soluble, n Al2O3 is insoluble