Chemistry: Post your doubts here!

[MysteRyGiRl]

ohh ur done wd ur ppr??how was it?? ppr 12 right?

 

[angelicsuccubus]

Worst chemistry practical, I've ever given .. I can't even believe how horrible my exam went ..p33 sucked.

 

[saudha]

Worst chemistry practical, I've ever given .. I can't even believe how horrible my exam went ..p33 sucked.

really...... was the pattern new..or new Qs

 

[Most_UniQue]

Worst chemistry practical, I've ever given .. I can't even believe how horrible my exam went ..p33 sucked.

I gave p33 also. It was awesome I answered each and every question correctly.

Moderator Edit : Paper Content

No discussion within 24 hours of the papers!

 

[Most_UniQue]

really...... was the pattern new..or new Qs

No , same questions. I found it easy

 

[angelicsuccubus]

really...... was the pattern new..or new Qs

no I just didn't read this one line and put the wrong solution in the burette... and after that everything just went wrong.. and usually I wouldn't mind.. but chem practicals were my favourite

 

[angelicsuccubus]

I gave p33 also. It was awesome I answered each and every question correctly. Btw what was your average volume of FA1 used in step 2? Mine was 25.1cm3

Moderator Edit : Paper Content

No discussion within 24 hours of the papers!

Oh wait.. are we not allowed to discuss?

 

[Most_UniQue]

if you want to save time then in the first titration attempt spend a little more time and measure exactly. Then just put a little higher value for rough titration and for accurate titrations 0.5 cm^3 up or down from exact. E.g If you get 23.5 first time then in rough you could use the value 24.2 and then in 1 st 2nd accurate titration you can write 23.50 and 23.00. Thats what I did today and still missed around 5 marks :/

Moderator Edit : Paper Content

No discussion within 24 hours of the papers!

 

[Most_UniQue]

Moderator Edit : Paper Content

No discussion within 24 hours of the papers! ?

Oh wait.. are we not allowed to discuss?

We cnt discuss oops.

 

[histephenson007]

Worst chemistry practical, I've ever given .. I can't even believe how horrible my exam went ..p33 sucked.

Not to worry, p33's weightage is only around 20%. If u can focus on P1 and P2 these few days, you can still get a very high score. Trust me, it happened to me last year.

 

[MysteRyGiRl]

my ppr went ALHAMDULILLAH realy gud

 

[Casablanca]

An organic compound has the following composition by mass:
C - 48.7%
H - 8.1%
O - 43.2%

Calculate the empirical formula.

How do you solve these kinds of questions? In MCQs I used to just do trial and error with the options, but how do you do it in structured? :/

Edit: nvm, figured it out myself.

 

[smzimran]

An organic compound has the following composition by mass:
C - 48.7%
H - 8.1%
O - 43.2%

Calculate the empirical formula.

How do you solve these kinds of questions? In MCQs I used to just do trial and error with the options, but how do you do it in structured? :/

Edit: nvm, figured it out myself.

First step:
Divide the percentages by the atomic masses of ELEMENTS

Second step:
Divide all the ratios by the smallest ratio

 

[Casablanca]

First step:
Divide the percentages by the atomic masses of ELEMENTS

Second step:
Divide all the ratios by the smallest ratio

Thanks. It confirms that I did it right.

 

[OmarALShamaa]

I got around 4cm3 for the second titration,
Any one got similar results!!!!!?

 

[Most_UniQue]

I got around 4cm3 for the second titration,
Any one got similar results!!!!!?

which paper??33?

 

[jrahmed]

The esterification reaction
ethanol + ethanoic acid --> ethyl ethanoate + water
is an equilibrium. The forward reaction is exothermic.
How can the value of the equilibrium constant KC be increased?
A by adding a little concentrated sulfuric acid as a catalyst
B by increasing the initial concentration of ethanol
C by lowering the temperature
D by raising the temperature

Ammonia is manufactured on a large scale by the Haber process.
In a particular plant, conditions of 400 °C and 250 atm in the presence of an iron catalyst are
used.
N2(g) + 3H2(g) 2NH3(g) ∆Ho = –92kJmol–1
What could contribute most to increasing the equilibrium yield of ammonia?
A adding more catalyst
B increasing the pressure to 400atm
C increasing the temperature to 1000°C
D using air rather than nitrogen
some one pls explain these question to me!

i guess explaining them now is useless

 

[saudha]

i guess explaining them now is useless

yup .... its use less.....

 

[Pals_1010]

Error carried forward? That means you still get the full marks for the next part? Even if the value in the first part is wrong?

 

[OmarALShamaa]

Yeah guys!!!!
Its paper 33!
I just dont now what went wrong!!?
I did exactly what the others did , but still ended up with this value!!
What might have went wrong!!
N whats the right answer!!!?