Chemistry MCQ thread...

[Zishi]

Q. Which of the following will not decolorize aqueous bromine?

A. Chlorine gas
B. ethene gas
C. FeSO4 aq
D. phenol aq.
E ethanal (liquid)

I guess ethanal. Again, phenols are in A2.

The answer given in book is chlorine gas

I guess I can't answer it, then. But I'm completely sure that ethanal doesn't decolorise aqueous bromine. :roll:

Q. Which of the following are true for conc sulfuric acid

1. ito oxidizes ethanoic acid
2. it dehydrates methanoic acid
3. it is reduced by potassium iodide

Well, WOW! I didn't know that my AS concepts may solve A2 questions. Well, as far as I know, the rate determining step is the slowest step of the reaction. That is the step in which cyanide ions attack the carbonyl group carbon atom.

way to go :good:

All are true, I believe.

 

[xHazeMx]

Q. Which of the following are true for conc sulfuric acid

1. ito oxidizes ethanoic acid
2. it dehydrates methanoic acid
3. it is reduced by potassium iodide

Well, WOW! I didn't know that my AS concepts may solve A2 questions. Well, as far as I know, the rate determining step is the slowest step of the reaction. That is the step in which cyanide ions attack the carbonyl group carbon atom.

way to go :good:

i think it is 1,2 and 3

 

[farrukh]

Q..
Fruit juices and fizzy drinks such as lemonade are often sold in aluminium cans. What is the most important reason why aluminium is the most suitable metal?

A. Al can be recycled
B. Aluminium has a very low density
C. Aluminium is most abundant metal in earth's crust
D. Aluminium is resistant to corrosion by acids
E. Aluminium is resistant to corrosion by water.

 

[farrukh]

Q. Which of the following are true for conc sulfuric acid

1. ito oxidizes ethanoic acid
2. it dehydrates methanoic acid
3. it is reduced by potassium iodide

Well, WOW! I didn't know that my AS concepts may solve A2 questions. Well, as far as I know, the rate determining step is the slowest step of the reaction. That is the step in which cyanide ions attack the carbonyl group carbon atom.

way to go :good:

i think it is 1,2 and 3

wrong..its 2 and 3....but how would it dehydrate methanoic acid?? i've not read of this reaction anywhre..

 

[xHazeMx]

Q..
Fruit juices and fizzy drinks such as lemonade are often sold in aluminium cans. What is the most important reason why aluminium is the most suitable metal?

A. Al can be recycled
B. Aluminium has a very low density
C. Aluminium is most abundant metal in earth's crust
D. Aluminium is resistant to corrosion by acids
E. Aluminium is resistant to corrosion by water.

E ?

 

[farrukh]

Q..
Fruit juices and fizzy drinks such as lemonade are often sold in aluminium cans. What is the most important reason why aluminium is the most suitable metal?

A. Al can be recycled
B. Aluminium has a very low density
C. Aluminium is most abundant metal in earth's crust
D. Aluminium is resistant to corrosion by acids
E. Aluminium is resistant to corrosion by water.

E ?

I answred the same but the answer key says D

 

[Zishi]

@Farukh: If that's the thing, then answer in book is wrong. It's because if you read brian OR other books, it says that conc phosphoric acid is better to use for dehydrating because conc. sulfuric acid is also an oxidising agent and it oxidises alcohols.

 

[Zishi]

Q..
Fruit juices and fizzy drinks such as lemonade are often sold in aluminium cans. What is the most important reason why aluminium is the most suitable metal?

A. Al can be recycled
B. Aluminium has a very low density
C. Aluminium is most abundant metal in earth's crust
D. Aluminium is resistant to corrosion by acids
E. Aluminium is resistant to corrosion by water.

E ?

I answred the same but the answer key says D

It's because we've to answer by remaining in the question's context. It says that "fizzy drinks" are often sold in aluminium cans. That, of course means that there are acids in it, and so most important reason is that it's resistant to acids.

 

[farrukh]

@Farukh: If that's the thing, then answer in book is wrong. It's because if you read brian OR other books, it says that conc phosphoric acid is better to use for dehydrating because conc. sulfuric acid is also an oxidising agent and it oxidises alcohols.

but how would it oxidize ethanoic acid??/
and how would it dehyrate methanoic acid?
HCOOH will convert to CO??

 

[Zishi]

@Farukh: If that's the thing, then answer in book is wrong. It's because if you read brian OR other books, it says that conc phosphoric acid is better to use for dehydrating because conc. sulfuric acid is also an oxidising agent and it oxidises alcohols.

but how would it oxidize ethanoic acid??/
and how would it dehyrate methanoic acid?
HCOOH will convert to CO??

Oops, sorry. Really sorry, I read your question's options as: Ethanol, methanol, etc.

So only options 2 and 3 are correct, because one is eliminated. We can't really oxidise ethanoic acid with conc H2SO4.

So in that case we remain with options 2 and 3. As for the explanation, I've no idea how methanoic acid is dehydrated.

 

[farrukh]

k...thanks fr ur help...i'll post a few more questions later

 

[Zishi]

k...thanks fr ur help...i'll post a few more questions later

Hmm, please do post AS questions. But if you're in A2, then you may make new threads for your A2 questions because this thread is currently only seen by AS students, I guess.

 

[xHazeMx]

the question about the concentrated sulfuric acid wasn't an AS question right?

 

[Zishi]

the question about the concentrated sulfuric acid wasn't an AS question right?

Right, it wasn't.

 

[xHazeMx]

RELIEEEF !!

 

[beststriker]

hey Guyz...i need help in Nov06/1 q12..!!

 

[sasukeuchiha]

hey Guyz...i need help in Nov06/1 q12..!!

It's C: the x-axis shows energy of molecules ( y-axis shows fraction of molecules with that energy) and at lower temperature more molecules will be at less energy.

 

[Abdulrab]

please do this ques from nov/06 Q1 !! thanx

 

[Abdulrab]

please do this question !!! i cant understand it !!

 

[Abdulrab]

how can we upload our questions here ??? i cant do it ! i hav many questions to ask !!! please help me !!