January Edexcel Chemistry IAL Unit 1 2016 (Thread)

Pretty sure I put the Br- lone pair. I hope it was butane, seriously don't want to get a B from an exam like this.

Do you remember the answer to this multiple-choice question: there were 3 compounds and a table of -ve values were given. I think they were copper sulphate, potassium something and potassium iodide.

Can sm1 tell me these answers plss.
what was the enthalpy change in the first part of the combustion question and what was the enthalpy change from the hess' cycle?
Why can't we decid which isomer was that with the three given data booklet values for the enthalpy change that 1 mark question.
and what was the percentage yield in the last question?

I only remember, these:

Hess cycle: -3030.5 kJ/mol

% yield: 73.5%

What was the reason for not being able to compare the data values or experimental values of the isomers?!

My Hess cycle answer was -3509.1 kJ/mol. This was the first vaue of one of the 3 enthalpies given on the opposite page, and i think that should be the answer because calculation from hess cycle should give the data booklet value not the experimental value.

I've seen similar questions, in past papers, in which you had to use your calculated value from simple Q=mct calculation, find delta H and use it in a hess cycle. (June 2013 is an example)

How can you say we had to use the first value on the opposite page? Those were the isomers given values.

No you didn't get me bro. I didn't say that you had to 'use' the value from the 3 given values. The value calculated from the hess cycle is equal to one of the values (the first one) given on the opposite page. I didn't use it at all. Its just a co-incidence that the value calculated is equal to that. In fact you can't use any value becuase the question asked us to 'calculate' the enthalpy change and thats why there was a table provided with the some of the enthalpy changes of formation and combustion of Hydrogen and carbon etc. required for the calculation. Thats why it was of 4 marks. We had to use the formula H(formation) = Sum of H(combustion) of elements - Sum of H(combustion) of compound. Honestly, I was also surprised to see the values match.. After being done with the calculation and seeing the enthalpy change matching with the data booklet value i was quite sure that I did it right..

YAASSSS exactly absolutely

I put the lone pairs of Br- and the arrow from a lone pair but i wanted to know if they deduct extra for extra lone pairs only on Br-. And do we always have to write names of compounds using IUPAC even if they havent stated? Why do i get this feeling full ums can really be at raw 80 😣 cos like u wanna get full ums but when its 80 its likee each mistake is super costly ya kni

Br- has only one lone pair so if u show any extra I guess they might deduct a mark and also a positive carbon atom in a carbocation can only bond with one pair of electrons.
They told us to identify by name or formula so IUPAC naming is not required but the two OH groups must be attached to the two carbon atoms that had the C=C double bond just broken
It all depends on the grade boundary. In some years students score full ums by getting more than just 70 and in others u must score full raw marks in order to get full ums

Oh finallyyyy smone who got the same!! I was so damn scared. this thread is filled with people who got -3030.5!! Virtual high 5!!!

umm quick question,
UK that MCQ that asked us to calculate number of double bonds in a compound and they tell us it reacted with this percent of hydrogen.... what did you guys get as an answer??? i got 2 as the answer

I got it 4