Chemistry: Post your doubts here!

[The Godfather]

Oh so you just always balance the electrons?
Thankyou!

To balance the half equations, you should balance the electron first then add the reactions.

 

[shazmina]

Help please ........
http://s11.postimg.org/980xvhyv7/table.jpg
The Ans is A......

This question please

 

[shazmina]

Why is the Ans B for this Question ...
http://postimg.org/image/nffgoopef/full/
I know that a boltzman distribution curve for a higher temperature has its peak shifted to the right, and in a lower height...
but here in option B the curve isnt shifted to the right eh?

 

[Metanoia]

This question please

Form a balanced equation for the reaction.

2NaCl + 2H2O --> H2 + Cl2 + 2NaOH

Then solve it as a mole calculations question.

Why is the Ans B for this Question ...
http://postimg.org/image/nffgoopef/full/
I know that a boltzman distribution curve for a higher temperature has its peak shifted to the right, and in a lower height...
but here in option B the curve isnt shifted to the right eh?

The answer seems to be D to me. Could you check the mark scheme again?

 

[The Godfather]

Why is the Ans B for this Question ...
http://postimg.org/image/nffgoopef/full/
I know that a boltzman distribution curve for a higher temperature has its peak shifted to the right, and in a lower height...
but here in option B the curve isnt shifted to the right eh?

It havent shifted to right, yes... :/

 

[The Godfather]

Form a balanced equation for the reaction.

2NaCl + 2H2O --> H2 + Cl2 + 2NaOH

Then solve it as a mole calculations question.



The answer seems to be D to me. Could you check the mark scheme again?

Answer is B. I checked it.

 

[Hiba shahid]

Yes
For example:
View attachment 54554

I meant what if above the blue line I write CH3 will that be right ??

 

[Hiba shahid]

Can a tertiary alcohol skeletal formula be written like this

 

[nehaoscar]

I meant what if above the blue line I write CH3 will that be right ??

No because in the skeletal formula you should not show any C's or C's attached to H's.
If it was OH or CN or something like that, then you'd show but not CH3

 

[nehaoscar]

Can a tertiary alcohol skeletal formula be written like this

Can't see image

 

[shazmina]

Form a balanced equation for the reaction.

2NaCl + 2H2O --> H2 + Cl2 + 2NaOH

Then solve it as a mole calculations question.


The answer seems to be D to me. Could you check the mark scheme again?

Thanks but i have a doubt .. is it like the 58.5 kg of NaCl only or does it include water as well?


I checked it many times and even now ... its B ...
Even i think the ans should be D but its B ... i even checked in the Examiners report ...

And i have seen you answering for the same question last year .. in this thread ... let me quote it for you

 

[shazmina]

W04qp1

Q5. You have to imagine yourself filling up the boxes with 8 electrons. If you follow the rules, you will end up with a final configuration that has the lowest energy level.

Q9. The short answer is, compared other organic compounds with the same number of carbons, burning a hydrocarbon usually gives use the most energy.
The C-O bonds for the rest require a bit more energy to break, compared to one that has only C-H single bonds.

Q11. No change in oxidation states for any atom, cant be redox reaction.

Q12. A boltzman distribution curve for a higher temperature with have its peak shifted to the right, and in a lower height.

Q18. For all the other options, there are dative bonds formed from nitrogen's lone pair.
A. N: -->C
B. N: -->H+
D. N: --> Ag+

Q38.

Y reflects the idea that ppt is formed faster than CH3CH2Cl which gives off 1 Cl- to precipitate with Ag+
1. Formed faster as it gives of 2 Cl-
2. Formed faster as C-Br bond is weaker, so Br- is released faster
3. Formed faster as C-I bond is weaker, so I- is released faster

This is the One .... Question 12 .. can u please check this out ...

 

[shazmina]

Answer is B. I checked it.

yea so what do you think?

 

[Metanoia]

Thanks but i have a doubt .. is it like the 58.5 kg of NaCl only or does it include water as well?


I checked it many times and even now ... its B ...
Even i think the ans should be D but its B ... i even checked in the Examiners report ...

And i have seen you answering for the same question last year .. in this thread ... let me quote it for you

The 58.5 kg is for NaCl (limiting reactant). The other reactant H2O is treated as an excess reactant.

I'll look at the W04 question and post here later.

At this moment, I am tempted to dismiss it as a typo in the marking scheme, because if the answer is indeed B instead of D, it would be wrongly answered by many students. This will mean that it would have to be discussed in the examiners' report (which it wasn't).

Furthermore, it was poor practice to present the options without putting the room temperature curve on the same axis for comparison. I believed they will be more careful about making it less ambiguous in recent years.

 

[Mathemagical]

why is 2 wrong?
More H+ concentration = more acidic ... so why is it wrong?

HCO2H dissociates into H+ and HCO2- ions, so there is only one mole of hydrogen ions per mole of methanol acid.

 

[shazmina]

The 58.5 kg is for NaCl (limiting reactant). The other reactant H2O is treated as an excess reactant.

I'll look at the W04 question and post here later.

At this moment, I am tempted to dismiss it as a typo in the marking scheme, because if the answer is indeed B instead of D, it would be wrongly answered by many students. This will mean that it would have to be discussed in the examiners' report (which it wasn't).

Furthermore, it was poor practice to present the options without putting the room temperature curve on the same axis for comparison. I believed they will be more careful about making it less ambiguous in recent years.

ohkkk thank you

Sure ... please check and let me know , thanks alot

 

[princess Anu]

ohkkk thank you

Sure ... please check and let me know , thanks alot

In D, the area doesn't look similar to the area given in the diagram of the question, it seems less.. therefore I promptly selected option B :s
Moreover, If you look closely, the graph given doesn't have its line extending beyond the x axis, whereas in B it is + the peak has displaced downwards showing that the graph has indeed moved rightwards & downwards ..

am I wrong Metanoia ?

 

[shazmina]

In D, the area doesn't look similar to the area given in the diagram of the question, it seems less.. therefore I promptly selected option B :s
Moreover, If you look closely, the graph given doesn't have its line extending beyond the x axis, whereas in B it is + the peak has displaced downwards showing that the graph has indeed moved rightwards & downwards ..

am I wrong Metanoia ?

ahan.... so thats the reason..

 

[mohhef3]

The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 – .
IO3 – + 2Cl – + 6H+ + 4e– → ICl 2 – + 3H2O I2 + 4Cl – → 2ICl 2 – + 2e– What is the ratio of IO3 – to I2 in the balanced chemical equation for the overall reaction?
A 1: 1 B 1 : 2 C 1 : 4 D 2 : 1
someone help me out with this que answer is b.its paper 12 nov 2013

 

[Metanoia]

In D, the area doesn't look similar to the area given in the diagram of the question, it seems less.. therefore I promptly selected option B :s
Moreover, If you look closely, the graph given doesn't have its line extending beyond the x axis, whereas in B it is + the peak has displaced downwards showing that the graph has indeed moved rightwards & downwards ..

am I wrong Metanoia ?

Honestly, its just as likely that D was the answer and we are running in circles trying hard to justify B.

If I assume they are plotted on the same scale, and overlay the two graphs....if B was really the intended answer, would it be fair for students to see the very very slight shift to the right?Maybe you are on to something with the focus on the area, but it can be optically misleading.
If I were to take the exam that year, I would honestly say I would have chosen D at that moment (and possibly gotten it wrong).

Lets just hope the paper for this year avoids such ambiguity.