The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

A-level Chemistry Revision Squad!

Scroll to see replies

Original post by mali473
For combustion you do reactants take away products. I rememeber this using the acronym CRAP or CAP ( combustion reactant takeaway products) CRAP sticks in my head aha

Posted from TSR Mobile


Thank you!!! The acronym is helpful too :biggrin:
can someone help me out on this question

Give the formula of an organic compound that forms an alkaline buffer solution whenadded to a solution of ethylamine. The answer is CH3CH2NH3Cl and I'm not sure why
Original post by seph_muriel
Thank you!!! The acronym is helpful too :biggrin:


Whenever you see combustion just think 'crap'

Posted from TSR Mobile
Original post by alow
Partial pressures of the different gases?


Ohh, why would you need that??? :redface:
Original post by chrisgul
can someone help me out on this question

Give the formula of an organic compound that forms an alkaline buffer solution whenadded to a solution of ethylamine. The answer is CH3CH2NH3Cl and I'm not sure why


It's normally the salt of your amine so yeah ... I suppose it is because of acid and their salt forming buffers?! :s-smilie::yep:

Posted from TSR Mobile
Reply 685
Avatar for alow
alow
19
Original post by FemaleBo55
Ohh, why would you need that??? :redface:


Because then you'd know how much of each gas there is.
Original post by voltz
For a titration, is the acid always in the burette or is the solution of unknown just always the base (in flask)?


I think the standard solution (the one you know the concentration of) goes in the burette and the unknown goes in the flask. Don't quote me on that tho :tongue:
organic question here !


Methyl butanoate, C5H10O2, is an ester used in the food industry to give products the flavour of apples.
structural formula: CH3C02CH2CH2CH3

Including methyl butanoate, how many structural isomers are there of C5H10O2 that are esters?
A) 6
B) 8
C) 9
D) 10
if anyone has doubts concerning the question ... let me know so I can explain the question in more detail....
thank u
:smile:
(edited 7 years ago)
Am making a whattsapp group for f334 and f335 ocr b salters. if interested DM me.
I have absolutely no idea on how to answer this question:
Suggest 2 reasons why standard enthalpy changes of combustion determined experimentally are less exothermic than the calculated theoretical values. (for 2 marks OCR Chemistry A) :s-smilie:
Original post by seph_muriel
I have absolutely no idea on how to answer this question:
Suggest 2 reasons why standard enthalpy changes of combustion determined experimentally are less exothermic than the calculated theoretical values. (for 2 marks OCR Chemistry A) :s-smilie:


Incomplete combustion so not everything has burned completely. And heat lost to surroundings

Posted from TSR Mobile
guys if your doing aqa try the a level papers not just AS because in the new spec papers there is stuff for paper 2 we can use especially in A Level Paper 3
Original post by mali473
Incomplete combustion so not everything has burned completely. And heat lost to surroundings

Posted from TSR Mobile


Why is it incomplete combustion?
How do you work this out please?
Compound F contains C, H and O only. O contains 54.2% oxygen by mass. Mr of F = 118 gmol-1
Show that the molecular formula of F= C4H6O4 [2 MARKS]
Original post by seph_muriel
Why is it incomplete combustion?


Not enough Co2 is available or other conditions not favourable for the reactants to combust
Original post by Hellper
Not enough Co2 is available or other conditions not favourable for the reactants to combust


Not enough Oxygen is available for the reactant to burn in

Posted from TSR Mobile
Original post by Hellper
Not enough Co2 is available or other conditions not favourable for the reactants to combust


Not enough oxgen is available to burn the reactant in therefore carbon monoxide, soot and water are produced as a result of this.

Posted from TSR Mobile
Original post by mali473
Incomplete combustion so not everything has burned completely. And heat lost to surroundings

Posted from TSR Mobile


I thought that that is to do with covalent character??
Original post by mali473
Not enough oxgen is available to burn the reactant in therefore carbon monoxide, soot and water are produced as a result of this.

Posted from TSR Mobile


Original post by bat_man
I thought that that is to do with covalent character??


yeah me too?
Original post by hafsa473
yeah me too?


yeah look at this.

Differences between theoretical and Born Haber (experimental)lattice enthalpies

The Born Haber lattice enthalpy is the real experimental value.When a compound shows covalent character, the theoretical and theborn Haber lattice enthalpies differ. The more the covalent characterthe bigger the difference between the values.

When the negative ion becomes distorted and more covalent we say it becomes polarised. Themetal cation that causes the polarisation is called more polarising if it polarises the negative ion.

Ionic with covalent character - The charge cloud is distorted .The theoretical and the experimental Born Haber lattice enthalpies will differ

100 % ionic - the ions are spherical.The theoretical and the born Haber latticeenthalpies will be the same

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you