Phys p12 and Chem p12- 9th and 10th June,2015 Tips!

[Aly Emran]

well trigonal pyramidal I guess man i keep forgetting this stuff .. Seriously you know a compiled note or something would be helpful ;(((

I didnt get it why? Isnt it triangular planar? Ah idk quick notes revision site :/
All am I doing is past pprs... And believe me, they are easy but i make a lot of silly mistakes... Lose around 8-12 marks normally

 

[Youknowwhoo]

I didnt get it why? Isnt it triangular planar? Ah idk quick notes revision site :/
All am I doing is past pprs... And believe me, they are easy but i make a lot of silly mistakes... Lose around 8-12 marks normally

Dude I got the notes on them but I need in detail nvm . But if you don't know the concept to spmehing you keep forgetting that's wot am saying playa :/ questions about what is the bond angle and bond shapes I got examples to them but I don't get the concept how is H3O+ less than 107.5 so how do you know / measure the angles ... lol

 

[Aly Emran]

Dude I got the notes on them but I need in detail nvm . But if you don't know the concept to spmehing you keep forgetting that's wot am saying playa :/ questions about what is the bond angle and bond shapes I got examples to them but I don't get the concept how is H3O+ less than 107.5 so how do you know / measure the angles ... lol

Oh thats VASEPR(dunno the exact format) law i guess:
Look.... Oxygen has 6 electrons in outershell.... It shares its 2electrons with Hydrogen.... That means 4electrons in outershell of oxygen left... H+ has no electrons so oxygen makes dative bond with H+ by providing 2electrons(4 use in bonding with 2H and 1H+).... Now oxygen has 2electrons(1 lone pair)

1 lone pair shows that angle is 107.5 or maybe less but if there was no lone pair, like if the structure wud be like this: H4O^2+[idk if it exists] it wud have been tetrahedral(109 angle)

This is all conceptual(VASEPR law)

 

[mohhef3]

Aluminium carbide, Al 4C3, reacts readily with aqueous sodium hydroxide. The two products of the

reaction are NaAlO2 and a hydrocarbon. Water molecules are also involved as reactants.

What is the formula of the hydrocarbon?

A CH4
B C2H6
C C3H8
D C6H12
someone explain this plz the answer is A

 

[Aly Emran]

Aluminium carbide, Al 4C3, reacts readily with aqueous sodium hydroxide. The two products of the

reaction are NaAlO2 and a hydrocarbon. Water molecules are also involved as reactants.

What is the formula of the hydrocarbon?

A CH4
B C2H6
C C3H8
D C6H12
someone explain this plz the answer is A

Al4C3+ 4NaOH +4H2O -----> 4NaAlO2 +3CH4 (C3H12(idk if it exists either) isnt in the option and none of these can form except for methane)
B and D are cancelled.... So A and left.... Sinc ethe qstn said that ONLY hydrocarbon and NaAlO2 are formed hence C cannot be the answer otherwise Hydrogen wud have evolved!

 

[mohhef3]

Al4C3+ 4NaOH +4H2O -----> 4NaAlO2 +3CH4 (C3H12(idk if it exists either) isnt in the option and none of these can form except for methane)
B and D are cancelled.... So A and left.... Sinc ethe qstn said that ONLY hydrocarbon and NaAlO2 are formed hence C cannot be the answer otherwise Hydrogen wud have evolved!
thx mate

thx mate

 

[Youknowwhoo]

Oh thats VASEPR(dunno the exact format) law i guess:
Look.... Oxygen has 6 electrons in outershell.... It shares its 2electrons with Hydrogen.... That means 4electrons in outershell of oxygen left... H+ has no electrons so oxygen makes dative bond with H+ by providing 2electrons(4 use in bonding with 2H and 1H+).... Now oxygen has 2electrons(1 lone pair)

1 lone pair shows that angle is 107.5 or maybe less but if there was no lone pair, like if the structure wud be like this: H4O^2+[idk if it exists] it wud have been tetrahedral(109 angle)

This is all conceptual(VASEPR law)

Thank you
Man do you see a pattern in CIE ? I do but there's always a question about something so you have to get the concept right !!? But I don't get the organic chem part pattern tho .. And the bond angle question is there amongst them the pattern but lol idk what am gonna do abt that and the organic chem too

 

[Aly Emran]

Thank you
Man do you see a pattern in CIE ? I do but there's always a question about something so you have to get the concept right !!? But I don't get the organic chem part pattern tho .. And the bond angle question is there amongst them the pattern but lol idk what am gonna do abt that and the organic chem too

First of all... Dont worry
Secondly concentrate on organic more... If u get a good grip in chem organic, u wont be scoring below than 30/40... Only 1 or 2 qstns out of so many organic are hard...but inorganic... I find inorganic tough... Especially the solubilities and the definitions like which shows that Water has H bonding- 1.Ice floats on water at 0 degree 2.Water has strong electronegative atom 3.surface tension .... These sort of qstns irritate me :/... Its not an official qstn though

 

[Youknowwhoo]

First of all... Dont worry
Secondly concentrate on organic more... If u get a good grip in chem organic, u wont be scoring below than 30/40... Only 1 or 2 qstns out of so many organic are hard...but inorganic... I find inorganic tough... Especially the solubilities and the definitions like which shows that Water has H bonding- 1.Ice floats on water at 0 degree 2.Water has strong electronegative atom 3.surface tension .... These sort of qstns irritate me :/... Its not an official qstn though

Well organic for me I never devoted time on it yesterday lol I took up the nomenclatures and learned them haha but didn't do that in time anyways man inorganic is no big deal you have to think of inorganic as less complicated .. Trust me that works haha CIE can't mess up that trust me

 

[Aly Emran]

Well organic for me I never devoted time on it yesterday lol I took up the nomenclatures and learned them haha but didn't do that in time anyways man inorganic is no big deal you have to think of inorganic as less complicated .. Trust me that works haha CIE can't mess up that trust me

I find organic comparatively easy... Inorganic is all shit... Damn so many silly mistakes u can make easily... But sometimes organic also ___ up
I hate last 10qstns tbh

 

[Devinky]

Memorise answers, read ER, spam past year papers since questions repeat a lot.
Doesn't help for long-term efficient studying but is the best way to secure an A.

 

[princess Anu]

Somebody help me with this question...pleasee..
Answer is B, I don't get why is C & D wrong

 

[slisjunknown]

The answer is D, but why not A?

 

[Aly Emran]

Somebody help me with this question...pleasee..
Answer is B, I don't get why is C & D wrongView attachment 54720

A wrong because lower temperature increases [SO3]
B correct because at low temperature, only the rate of reaction will be slow and less particles will possesss the LOWERED activation energy.
C wrong because Nitrogen oxides are impurities in the reaction and again both gasses need to be separated from each other which is expensive compared to using V2O5. Both are gasses so they need to be separated.
D wrong because extremely high temperature result in less production of SO3(equilibrium shifts to left) although rate of reaction will increase

View attachment 54731
The answer is D, but why not A?

not A because look carefully, at 2 terminal, the current splits and moves back to the battery while the remaining current moves to the 3terminal(krichoff's 1st law)

 

[princess Anu]

A wrong because lower temperature increases [SO3]
B correct because at low temperature, only the rate of reaction will be slow and less particles will possesss thw LOWERED activation energy.
C wrong because Nitrogeoxides is an impurity in the reaction and again both gasses need to be seperated from each other which is expensive compared to use V2O5. Both are gasses so they need to be separated.
D wrong because extremely high temperature result in less production of SO3(equilibrium shifts to left) although rate of reaction will increase

not A because look carefully, at 2 terminal, the current splits and moves back to the battery while the remaining current moves to the 3terminal(krichoff's 1st law)

Hey, thanks for the explanation!
One thing I donot understand is.. which gases are you referring to? & why do they need to be separated?
Thanks again

 

[Aly Emran]

Hey, thanks for the explanation!
One thing I donot understand is.. which gases are you referring to? & why do they need to be separated?
Thanks again

NO2 and SO3 both are acidic gases. If we dont separate them, nitic acid and sulphuric acid both will be formed... Both are colourless solutions so both are difficult to remove and maybe yield of SO3 can also be disturbed. Plus this NO2 ans SO2 is used in atmosphere to form acid rain.... Contact process only includes use of Heterogenous catalyst while the production of acid rain in atmosphere requires a Homogenous catayst
Anytime

 

[princess Anu]

NO2 and SO3 both are acidic gases. If we dont separate them, nitic acid and sulphuric acid both will be formed... Both are colourless solutions so both are difficult to remove and maybe yield of SO3 can also be disturbed. Plus this NO2 ans SO2 is used in atmosphere to form acid rain.... Contact process only includes use of Heterogenous catalyst while the production of acid rain in atmosphere requires a Homogenous catayst
Anytime

right.. but how does that explain y C is wrong?

 

[slisjunknown]

A wrong because lower temperature increases [SO3]
B correct because at low temperature, only the rate of reaction will be slow and less particles will possesss the LOWERED activation energy.
C wrong because Nitrogen oxides are impurities in the reaction and again both gasses need to be separated from each other which is expensive compared to using V2O5. Both are gasses so they need to be separated.
D wrong because extremely high temperature result in less production of SO3(equilibrium shifts to left) although rate of reaction will increase

not A because look carefully, at 2 terminal, the current splits and moves back to the battery while the remaining current moves to the 3terminal(krichoff's 1st law)

Thanks a lot........

 

[princess Anu]

not A because look carefully, at 2 terminal, the current splits and moves back to the battery while the remaining current moves to the 3terminal(krichoff's 1st law)[/QUOTE]

Isn't A wrong because terminal 1 & 3 are not connected in the first place? so the circuit is not complete? correct me If I'm wrong

 

[Aly Emran]

right.. but how does that explain y C is wrong?

Im so sorry i didnt read the qstn properly
Its like this:
First of all he asked "What affects the choice of conditions for this reaction"
A mentions wrong change
B mentions correct change
C doesnt affect the choice because no need of additional catalyst... Adding a catalyst doesnt change the [SO3] . it only increases rate of reaction.
D also mentions wrong change...