chemistry atp

[Qasim Hafeez]

It was 16.11g. And pipette (pipette measures 25cm3 or 50cm3; measuring cylinder above 100cm3 accurately).

btw do you remember the titration readings in those three pipette? initial and final readings?

 

[huraira5]

what was the colour change? green to purple?

 

[Eman Shahid]

the first and third reading were to be ticked right?

Yeah, it was the first and third one to be ticked. I got that wrong, and the average value, there goes my two marks.

 

[sharjeelmumtaz]

It was 16.11g. And pipette (pipette measures 25cm3 or 50cm3; measuring cylinder above 100cm3 accurately).

16.11? What question was that?

 

[FayadC]

The one where you had to subtract the initial mass from the final mass. At the initial stages of the titration thing.

 

[Shafin Ahmed]

A

I made a mistake on the first part of the titration, I calculated the average volume wrong, I lost one mark there. Because of that my whole titration could be wrong, so will there be an Error Carried forward(e.c.f)?

Are you from Bangladesh or Pakistan bro ? And yes there is ECF applicable, you will get all the marks for the next questions if you do those right using the wrong value

 

[Shafin Ahmed]

my answer was 8.2g but majority of my friend's answer was 1.8g

8.2g is the answer. Question is how much left ? 10-1.8=8.2

 

[Shafin Ahmed]

what was the colour change? green to purple?

Its green to purple, I wrote red brown at first then wrote green. I was confused when only 2-3 students wrote this answer and all my friends wrote colourless to purple.

For graph, one was 0.x and another was 8.x forgot exact values

 

[Rizwan Javed]

Do you mean C2H5OH for X and C4H9OH for Z? I wrote the same thing.

sorry you got it wrong. Your answers are correct but you swapped them. C4H9OH was for X and C2H5OH for Z. Because smaller alcohol molecules give a larger temp rise.

 

[Shafin Ahmed]

sorry you got it wrong. Your answers are correct but you swapped them. C4H9OH was for X and C2H5OH for Z. Because smaller alcohol molecules give a larger temp rise.

Sorry bro, FayadC got it right. As number of C atoms increase the energy released per mole increases.

 

[Hamza Jawad]

Sorry bro, FayadC got it right. As number of C atoms increase the energy released per mole increases.

Yup, you're right. So the one with lower temp. rise was the one with lower Carbon number right? And did it matter if we wrote the formula as e.g C4H9OH or C4H10O?

 

[Bilal Mir]

No. The question didn't require us to write the formula. If you had written Ethanol and Butanol instead ,it would be fine too..

 

[Shafin Ahmed]

Yup, you're right. So the one with lower temp. rise was the one with lower Carbon number right? And did it matter if we wrote the formula as e.g C4H9OH or C4H10O?

That would be fine I guess

 

[Hamza Jawad]

Also, about the colour change, one of my most 'intelligent' friend claims that Green to purple was indeed the correct answer but colourless to purple/pink/(Shades of purple for KMnO4) were acceptable as well. Can anyone verify that?

 

[Rizwan Javed]

Also, about the colour change, one of my most 'intelligent' friend claims that Green to purple was indeed the correct answer but colourless to purple/pink/(Shades of purple for KMnO4) were acceptable as well. Can anyone verify that?

in one of the previous papers, a same question had been asked. So in the marking scheme both were regarded as acceptable in that case; so hope for the best that this time they also include this option.

 

[Rizwan Javed]

SEE THIS Hamza Jawad

 

[Hamza Jawad]

SEE THIS Hamza Jawad
View attachment 53789 View attachment 53791

Yeah thanks a lot for the confirmation. I wrote colourless to pink from memory, possibly i had attempted the paper you shared here.

 

[Rizwan Javed]

Yeah thanks a lot for the confirmation. I wrote colourless to pink from memory, possibly i had attempted the paper you shared here.

welcome do pray for me as well; I'm appearing for 10 subjects.

 

[Hamza Jawad]

welcome do pray for me as well; I'm appearing for 10 subjects.

Wow. Sure. 10's gonna need a lot of prayers. Best of luck!

 

[Shafin Ahmed]

SEE THIS Hamza Jawad
View attachment 53789 View attachment 53791

The question was different. In M/j 15 it said, what is the colour , BEFORE P is ADDED ________ and At end Point ___________

Before P ( potassium Mang.) is added the solution cant be colourless. It would be the natural colour of Fe2SO4 (green salt)

Before P is added, its green.When P is added it becomes colourless but when excess it becomes purple.

Anyways, I cant say for sure. Need to see MS when it comes out