Chemistry: Post your doubts here!

[fantastic girl]

Yes, the question is on balancing reactions. Option A is the only hydrocarbon that can balance the reaction.

Thanks alot
i thought i was being stupid xP
so there's no other way to find out ryt?

 

[nehaoscar]

http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_12.pdf
Can someone tell me how to find the answer for Q6 ? :/
A is the answer
is it like we see if the equation is balancing wid each hydrocarbon ? xP
in that case its only A i think.

Yes:
The equation will be
Al4C3 + 4NaOH + 4H2O = 4NaAlO2 + 3CH4
This requires a bit of trial and error

firstly writing without balancing will give
Al4C3 + NaOH + H2O = NaAlO2 + CH4

Now pop a 4 in front of NaAlO2 so the Al's balance and a 4 at NaOH so the Na balances and a 4 at H2O so the O's balance too.
Al4C3 + 4NaOH + 4H2O = 4NaAlO2 + ?

Now we see that there are 3C's and 12H's left over
C3H8 is not possible as then H's don't balance
C2H6 is also not possible
So the only option is 3CH4

 

[nehaoscar]

Both alcohols and carboxylic acids react with sodium metal. Follow these links for further information:
Alcohols: http://tinyurl.com/bawcd94
Carboxylic acid: http://tinyurl.com/5r72ms

However, only carboxylic acids react with sodium carbonate in a neutralisation reaction, not alcohols. The above link has further information about this. Hope this helps!

Alright! Thanks!
And which of the two react with NaOH?

 

[Mathemagical]

Alright! Thanks!
And which of the two react with NaOH?

NaOH is basic, so carboxylic acids would react with it. However, alcohols would not.

 

[nehaoscar]

Does an ester react with HCN? If yes then please can you give an example with structural or displayed formula?

 

[Mathemagical]

Does an ester react with HCN? If yes then please can you give an example with structural or displayed formula?

No, they do not react.

 

[nehaoscar]

NaOH is basic, so carboxylic acids would react with it. However, alcohols would not.

What about aldehydes and ketones reacting with Na, NaOH and NaHCO3?

 

[Mathemagical]

What about aldehydes and ketones reacting with Na, NaOH and NaHCO3?

Aldehydes and ketones would not react with any of those.

 

[nehaoscar]

How is it A?
B has 3 outer shell e- and each will bond to an F...

 

[Mathemagical]

This is a useful diagram you can refer to.

 

[Mathemagical]

View attachment 54270
How is it A?
B has 3 outer shell e- and each will bond to an F...

A complete outer shell has 8 valence electrons, whereas Boron only has 6 in BF3.

 

[nehaoscar]

Does the equilibrium position affect the rate of reaction?
I'm sure it only affects the yield right?

 

[nehaoscar]

A complete outer shell has 8 valence electrons, whereas Boron only has 6 in BF3.

Then what about B and D? how many electrons do they have in their outer shells?

 

[nehaoscar]

How to do this one? Answer is B

 

[Mathemagical]

Does the equilibrium position affect the rate of reaction?
I'm sure it only affects the yield right?

You're asking the wrong questions here. For every change in temperature, pressure or some other condition you have to know that it may affect one or both of the equilibrium or rate. The answer is D because removing ammonia would not alter the rate, whereas increasing the temperature and pressure would.

 

[nehaoscar]

Answer is C ... how?

 

[Mathemagical]

View attachment 54272

How to do this one? Answer is B

For this, I suggest learning the ICE Tables Method. Here's the link for it: http://tinyurl.com/lv2hlh9

 

[nehaoscar]

Why C? Why not A or B?

 

[nehaoscar]

You're asking the wrong questions here. For every change in temperature, pressure or some other condition you have to know that it may affect one or both of the equilibrium or rate. The answer is D because removing ammonia would not alter the rate, whereas increasing the temperature and pressure would.

But the question specifies forward reaction rate.
Since it is exothermic reaction, wouldn't increasing the temperature increase the backward reaction rate?

 

[Mathemagical]

View attachment 54273
Answer is C ... how?

The question states that vigorous effervescence occurred, so naturally I would opt for C, because Barium is the most reactive element amongst the other choices.