Aqa chem 4/ chem 5 june 2016 thread

Please can you explain q4a Jan -12 I really don't know where the answer came from

But sometimes both species are present in two different reactions , so how would I know?


Posted from TSR Mobile

Does anyone know why vdw forces act between terylene molecules instead of hydrogen bonding?

Posted from TSR Mobile

This is great but I lose it when is comes to 1/2 X moles of H+ neutralise 1/2x moles of OH-

would you be able to substitute some made up random simple numbers in it and exemplify?

Thankyou, sorry to be a pain!

http://filestore.aqa.org.uk/subjects/AQA-CHEM4-QP-JUN12.PDF

8b please

Alkenes react with aqueous bromine, alkanes don't.

C_nH_2n is either an alkene or cycloalkane.

Thanks

Do you mind quickly explaining the use of chromotography? and what q7b is on about?
What do we have to know about it?

Chromatography is a method of seperating similar compounds.

Alcohols are more polar than ketones due to the O-H bond being much more polar than the C=O bond. In column chromatography there is a stationary phase (silica) and the mixture of compounds is carried by the mobile phase which is a solvent. Each compound has a different affinity for the stationary phase. A greater affinity means it will take longer to reach the bottom of the column because there is a stronger attraction to the stationary phase. Propanol has the greater affinity for the stationary phase because it is more polar and hence a greater retention time, meaning propanone is the first to leave the column.

Chromatography is a method of seperating similar compounds.

Alcohols are more polar than ketones due to the O-H bond being much more polar than the C=O bond. In column chromatography there is a stationary phase (silica) and the mixture of compounds is carried by the mobile phase which is a solvent. Each compound has a different affinity for the stationary phase. A greater affinity means it will take longer to reach the bottom of the column because there is a stronger attraction to the stationary phase. Propanol has the greater affinity for the stationary phase because it is more polar and hence a greater retention time, meaning propanone is the first to leave the column.

Do you mind listing the type of chromotography's and the stationary/liquid phases:

Is GLC: Stationary - liquid
mobile - inert gas

IDk what other types there are?

Edit: what does affinity mean sorry lol

Column:
Stationary - Silica gel.
Mobile - Solvent

GLC:
Stationary - powder coated with oil.
Mobile - unreactive gas (i.e. Nitrogen/Helium)

They're the only 2 we need to know I think.

Affinity in this case means the attraction to the stationary phase. Think of it like a magnet, the different compounds have a different affinity - or in this analogy - stronger and weaker attractions to the magnet. This leads to the compounds leaving the column at different times.

What sort of qs do you normally get asked?

For every 2mol of SO₃ that breaks down, 2mol of SO₂ and 1 mol of O₂ are formed. We're not saying that some SO₃ breaks down to form SO₂ and some breaks down to O₂, it's that each mole of SO₃ that breaks down forms one mole of SO₂ AND half a mole of O₂.

It's usually just why one leaves the column first from the papers that I've done.

The 2015 paper was a joke