Chemistry: Post your doubts here!

[sukasukinya]

How to do this? Im having paper 1 in 3 days and stressing out right now because of this question:'( Help

 

[A*****]

View attachment 63820
How to do this? Im having paper 1 in 3 days and stressing out right now because of this question:'( Help

I think this is removed from the syllabus

 

[Kanekii]

View attachment 63820
How to do this? Im having paper 1 in 3 days and stressing out right now because of this question:'( Help

Its C?

 

[sukasukinya]

Its C?

The answer is D

 

[Hamnah Zahoor]

View attachment 63820
How to do this? Im having paper 1 in 3 days and stressing out right now because of this question:'( Help

The answer is D

I guess the examination report explain it enough

Question 28: The correct answer was D. The most commonly chosen incorrect answers were A and B. These answers, A and B, both have compound X having a cyclopentane ring which would have to be opened by the reaction with ammonia. This will not occur. Compound X must be 1,5-dibromooctane. The reaction of 1,5-dibromooctane with ammonia takes place by nucleophilic substitution in two steps. In the first step of the reaction an –NH2 group substitutes for one of the bromine atoms. Since this –NH2 group has a lone pair it can attack the δ+ carbon atom of the second C-Br by the same nucleophilic mechanism, giving coniine as the organic product.

 

[khadijaimran]

ans is D?

 

[khadijaimran]

this one as well. the ans is B

 

[A*****]

How is it 5?

 

[A*****]

this one as well. the ans is B

Enthalpy change of reaction= 3(+111) + (+822) +3(-394) = -27
55.8g is 1 mole. Since ΔH for this reaction is for 2 moles, so divide it by 2 to get -13.5

 

[Hamnah Zahoor]

How is it 5?

I didn't included the hydrogen to make it more clear.

 

[Hamnah Zahoor]

ans is D?

Apart from guess work i mean trying the options one by one I can not find any other way.
X + H2O------>Al(OH)3 + hydrocarbon gas(HC)..unknown
HC(g) + O2------>H2O + CO2

cancel out the hydrocarbon and water molecules from both side of the equations to make it an overall equation

considering option D.

Al4C3 + 9O2+ 12H+ ------>4Al(OH)3 + 3CO2
mol of CO2=108/24000=4.5*10-3
3:1.......mol of Al4C3=1.5*10-3
Mr=144
option D is correct.

 

[A*****]

I didn't included the hydrogen to make it more clear.
View attachment 63829

Thanx!

 

[Hamnah Zahoor]

Thanx!

No problem

 

[khadijaimran]

Enthalpy change of reaction= 3(+111) + (+822) +3(-394) = -27
55.8g is 1 mole. Since ΔH for this reaction is for 2 moles, so divide it by 2 to get -13.5

thankyou

 

[khadijaimran]

Apart from guess work i mean trying the options one by one I can not find any other way.
X + H2O------>Al(OH)3 + hydrocarbon gas(HC)..unknown
HC(g) + O2------>H2O + CO2

cancel out the hydrocarbon and water molecules from both side of the equations to make it an overall equation

considering option D.

Al4C3 + 9O2+ 12H+ ------>4Al(OH)3 + 3CO2
mol of CO2=108/24000=4.5*10-3
3:1.......mol of Al4C3=1.5*10-3
Mr=144
option D is correct.

thanks a lot

 

[Hamnah Zahoor]

thanks a lot

You are welcome.

 

[MShaheerUddin]

View attachment 63810


Plz someone guide me on how to balance such equations...will be really grateful

Is this As level or A level?

 

[A*****]

Is this As level or A level?

As

 

[MShaheerUddin]

When BaCO3 and MgCO3 are heated they would produce their oxides, right?
and If they react with HCL then they wouldn't produce CO2 .. I think 1 is wrong but it isn't .. why?

 

[A*****]

View attachment 63850
When BaCO3 and MgCO3 are heated they would produce their oxides, right?
and If they react with HCL then they wouldn't produce CO2 .. I think 1 is wrong but it isn't .. why?

Barium carbonate does not decompose on heating using a busen burner