OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

No

Initial rate of reaction decreases in first 200 seconds since less particles per unit volume hence frequency of effective collisions decreases?

Surely there is only one 'initial rate of reaction' and it has one value.

Yeah I mean rate. For that 2 marker about why it decreases in first 200 secs

Then you are likely to get the marks.

Cheers, sorry for all the questions

when you name the molecule doesnt the bromo come before the methyl and when there are 2 methyls isnt it dimethyl because i got something like that

Please feel free to stalk my previous posts and prove yourself incorrect. Goodbye.

Happy?

Yawn. Get back to me on 18th August.

Why should I get back to you? What's my grade to you? And how does that answer what the question asked?

He posted a pic of the paper. Call it a day


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No problem. As it's a forum it's up to me whether I answer anyway.

No problem. As it's a forum it's up to me whether I answer anyway.

also do you think the boundary will be less than 80% for an A since last year it was 46/60 and 78/100 which is 77.3% and it is new spec and with all content assessed in 1 exam so around 76%? Thank you

It is impossible to say. Don't waste time even thinking about this. I, and all of my students, thought the papers were both very fair.

hey

would we still get 2 out of 3 marks if we draw an incorrect tangent but use change in Y over change X to get the gradient for the rates question?

And for the experiment question I wrote something like:
place container and contents on mass balance and start timer and keep noting down mass after every 30 seconds and do it for 10 mins but make sure it is calibrated beforehand and then do 3 repeats and find mean average mass lost and then use that to find mean average rate of reaction? How many out of 3 marks do you think I have got? Thanks a lot!!

just worried that I may just miss out on an A if it's 80%... and I need an A* prediction but yes it is done now and I can't change it

There will no doubt be a range for the tangent value. There will be a mark for showing it on the graph.

The question required you to measure the volume of gas evolved. Does your method do this?