ocr chemistry past paper questions

in f324 january 2012 paper the stationary phase used is an alkane, and basically the answer is that alcahols would be more soluble than another alkane with the stationary phase

i know this is because alcahols can form hydrogen bonds but the stationary phase isnt water its an alkane so how does that principle work?

also in f325 january 2011 q7bii how are you suppose to know the gas compound formed, from what i can guess its just by randomly fiddling around with chemical involved.
and in part ii of b when they balance the equation the NO doesnt have a charge, shhouldnt it be +1,
also my answer basically was half everything except the iodine, and they balalnced the answer (to balance the charges) by multiplying everything by x2 except the iodine, why isnt iodine x2 aswell, the way the equation is its like iodine doesnt really take part.

ive got plenty more questions lol if anyone can help out it would be appreciated.

Reply 1

Pigster

Short chain alcohols are especially soluble in alkanes, but longer ones are. Do you know why?

How many colourless gases have a molecular mass of 30, starting with those reactants? Gases can't made of solitary ions (it can't just be NO+), also at RTP (assumed) there are no ionic gases.

What are the two half equations? I- -> I2 and NO2- -> ??? (NO), also OH- has to be a product

Reply 2

nmjasdk

Original post by Pigster

yeah shorter ones are more soluble because more of the molecule is bonded to the water, but how can hydrogen bonds form with alkanes to become soluble?

why cant the gas be ionic the N is +3 and the o is -2 so overall charge should be +1

also i dont get what you mean by the half equation thing because their is no half equations in the questionis and i understood the reactants and products but why isit that the equation doesnt even depend on the iodine if you look at it its as if iodine isnt reacting with the other stuff, thats why you can multiple the other reactants and products by a 100 and the iodines can still be 2I- ----> I2

Reply 3

Borek

Original post by Pigster

Short chain alcohols are especially soluble in alkanes, but longer ones are.

Either my English fails me, or you missed "not" somewhere.

Reply 4

Pigster

Poop. In my defence I am poorly at the moment. I probably should say away from here if I'm going to type rubbish.

To clarify: short chains aren't especially soluble in alkanes, but longer ones are. Since long ones are more soluble in alkanes, their retention time will be longer and hence your mixture will separate.

You can have an NO+ ion, but what negative ion would you have? Regardless, what do oppositely charged particles do? Do you know of any ionic substances that do not form crystals? i.e. ionic substances cannot be gases at RTP.

You should create the half equation yourself, if not given in the question. You start with NO2- and end up with NO, also OH- is a product.

ocr chemistry past paper questions

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you