Chemistry: Post your doubts here!

[Metanoia]

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can anyone pls explain me how to solve these two questions

First question was explained in #17975

For the 2nd question,
moles of ethanol = 2.3/46 = 0.05 mol
moles of ethanoic acid expected = 0.05 mol
mass of ethanoic acid expected = 3 g
actual mass obtained = 60% x 3 g = 1.8 g

 

[A*****]

CO2 does not have pd-pd interaction as it has no overall dipole moment

But due to difference in electronegativities, it DOES have dipoles...so won't there b pd-pd forces due to the presence of dipoles, despite the fact that it has no dipole moment ?

 

[sukasukinya]

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

 

[A*****]

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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]

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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]

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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.
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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]

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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