OCR GCSE Chemistry A- C7 + Ideas In Context, May 24th 2012. OFFICIAL THREAD

Heyy.. this is 21st Century, right? 2006 spec? If so, that's what I'm doing.

I seriously need to revise the C2 polymers for the IIC.

I actually need to start revising for C7...

We need a pool of questions here guys.. I'm willing to exchange literally hundreds of Biology/Physics questions in return! X

Questions for the Ideas in Context... the plasticisers in our case.

I'm bricking it.
Those questions look scary. I can't get my head around interpreting results from a titration ( finding the concentration/mass of something using relative formula mass and titration results)
My teachers refusing to explain it, I would appreciate if anyone helped me, I'm completely lost.

I'll attept to help you but I don't know if I'll be much help cause it's hard to explain typing lol.

First of all it's sooo much easier if you lay it out in an organised way. I always write the formulas for the two things your using (eg ethanoic acid and sodium hydroxide) at the top, down the side I write Volume, mass and concentration. so it kind of looks like a table, then I read through the question and fill in what information I know.

Then if I know a volume and it's in cm3 I'll convert it to dm3 (divide it by 100) so I don't forget too, as concentration is in g/dm3.

Then you should have 2 of 3 things down the side filled in (concentration, mass, volume) so you can work out the missing on using the formula mass = concentration x volume.

Once you have all 3 things, work out the relative formula masses of the 2 solutions your using. (do you know how to do this?). then use the side you know everything of to work out things for the other side, it's basically ratio. you can use the go through one method. for example if you wanted to find the mass of ethanoic acid, and you knew the mass of sodium hydroxide was 0.00232g you'd work out the RFM which is 40 for sodium hydroxide you'd then divide 40 by 40 to get it to 1 then times it by 0.00232 then you'd do the same to the other side - work out the RFM of ethanoic acid which is 60 then divide it by 40 times it by 0.00232 (as thats what you did to the other side) and then you finally have you answer!

Like I said it's hard to explain typing, but I hope this has helped!

I'll attept to help you but I don't know if I'll be much help cause it's hard to explain typing lol.

First of all it's sooo much easier if you lay it out in an organised way. I always write the formulas for the two things your using (eg ethanoic acid and sodium hydroxide) at the top, down the side I write Volume, mass and concentration. so it kind of looks like a table, then I read through the question and fill in what information I know.

Then if I know a volume and it's in cm3 I'll convert it to dm3 (divide it by 100) so I don't forget too, as concentration is in g/dm3.

Then you should have 2 of 3 things down the side filled in (concentration, mass, volume) so you can work out the missing on using the formula mass = concentration x volume.

Once you have all 3 things, work out the relative formula masses of the 2 solutions your using. (do you know how to do this?). then use the side you know everything of to work out things for the other side, it's basically ratio. you can use the go through one method. for example if you wanted to find the mass of ethanoic acid, and you knew the mass of sodium hydroxide was 0.00232g you'd work out the RFM which is 40 for sodium hydroxide you'd then divide 40 by 40 to get it to 1 then times it by 0.00232 then you'd do the same to the other side - work out the RFM of ethanoic acid which is 60 then divide it by 40 times it by 0.00232 (as thats what you did to the other side) and then you finally have you answer!

Like I said it's hard to explain typing, but I hope this has helped!

Hey, cm3 to dm3 is divided by 1000, not 100. Good explination though, thank you.

Wow, thanks
I kind of understand that, I'll work on it. Either way, it's a much better explanation compared to my teacher...
I really apreciate it