Chemistry: Post your doubts here!

[Hamnah Zahoor]

Plz can u explain those 2 qs?

I am sorry I just went offline minutes before you asked me but still I beleive I am not late
Q: 1 you asked is solved at the following website
http://chem-solutions-9701.blogspot.com/2016/11/chemistry-doubts-970111mj14.html
2 moles of a single product is formed just divide the formula of compound by 2
For question :2
For greatest amount of energy to be released the compound should not have oxygen in it or least amount for maximum energy released.
From examination report:
Question 9 Candidates were given four compounds – CH3CH2CH3 and three of its oxidation products, CH3CH2CH2OH, CH3COCH3 and CH3CH2CO2H – and asked which would release the greatest amount of energy on complete combustion. 40% of candidates gave the correct answer (propane itself), the others presumably not appreciating that every stage in the oxidation process would be exothermic, and that therefore the earliest point in a sequence of oxidations would yield the highest energy release. An alternative approach to this question would have been to make use of the table of bond energies within the Data Booklet, leading to the same conclusion. Rather surprisingly four questions had a facility below the design limit of 25%, i.e. below the ‘guessing level’, and the reasons for this were clearly very varied.

 

[Hisham Khan]

Isin't the answer D?

 

[A*****]

I am sorry I just went offline minutes before you asked me but still I beleive I am not late
Q: 1 you asked is solved at the following website
http://chem-solutions-9701.blogspot.com/2016/11/chemistry-doubts-970111mj14.html
2 moles of a single product is formed just divide the formula of compound by 2
For question :2
For greatest amount of energy to be released the compound should not have oxygen in it or least amount for maximum energy released.
From examination report:
Question 9 Candidates were given four compounds – CH3CH2CH3 and three of its oxidation products, CH3CH2CH2OH, CH3COCH3 and CH3CH2CO2H – and asked which would release the greatest amount of energy on complete combustion. 40% of candidates gave the correct answer (propane itself), the others presumably not appreciating that every stage in the oxidation process would be exothermic, and that therefore the earliest point in a sequence of oxidations would yield the highest energy release. An alternative approach to this question would have been to make use of the table of bond energies within the Data Booklet, leading to the same conclusion. Rather surprisingly four questions had a facility below the design limit of 25%, i.e. below the ‘guessing level’, and the reasons for this were clearly very varied.

Tysm but can u guide me a lil bit more regarding q2 using bond energies, how we will determine that? The extra C-H bond has the smallest value so what does it mean?

 

[A*****]

View attachment 64042
Isin't the answer D?

It is B...2nd is also correct since it is an anti oxidant

 

[Hisham Khan]

It is B...2nd is also correct since it is an anti oxidant

yes it does remove sour taste but I have schemes with this not as correct only anti oxidizing or reducing property and stop growth of aerobic bacteria are considered correct toh

 

[A*****]

How did it go guyz?

 

[Hisham Khan]

How did it go guyz?

Too many orgies but it went good .
Inorganic was easy I had 5-6 tokas in oganic and 5 of them are correct lollll

 

[Hisham Khan]

How did it go guyz?

Q39 was cracking and dehydrogenation right???

 

[Hisham Khan]

Nitrogenwas -1 and other option was +4

 

[Hisham Khan]

many questions were repeat even from compiled questions lol

 

[Hisham Khan]

enthalpy was -144 and limestone was 528 or something.They were repeated.I didnt even know how to do them lmao but got them correct

 

[A*****]

Q39 was cracking and dehydrogenation right???

One was cracking but I don't remember the other one...all I remember is that the one with ethanol was not supposed to be included

 

[A*****]

Nitrogenwas -1 and other option was +4

I think so

 

[A*****]

What was the emperical formula of J?

 

[SohaibButt]

One was cracking but I don't remember the other one...all I remember is that the one with ethanol was not supposed to be included

Hey what was it's answer the one with hot naoh n cold naoh?

 

[SohaibButt]

What was the emperical formula of J?

D

 

[Mts.99]

what was the answer to ques where they said reaction was done without catalyst and increased temp.. options were
Activation energy increases
activation energy decrease
no. collision increase? dont remember the 4th one lol

 

[Hisham Khan]

One was cracking but I don't remember the other one...all I remember is that the one with ethanol was not supposed to be included

one was oxidation other dehydrogenation and other cracking.C was correct .Oxidation of cohol was wrong

 

[SohaibButt]

enthalpy was -144 and limestone was 528 or something.They were repeated.I didnt even know how to do them lmao but got them correct

It wS C?

 

[A*****]

And what was that distinguishes bw the two by alkaline iodine?