I really need someone's help. I have my mock coming up this monday!
I seem to be failing in literally everything, i'm not sure if its because i don't understand or don't know the knowledge. However i'm starting to get really worried and was wondering if any of you know how to cope studying Chemistry or have done a mock for this exam board :(this year! As this can really help me when preparing for the actual exam.
Since i don't have much responses will be useful anytime now :huh:
I don't know about the specific requirements of the OCR exam but the basic plan is the same for all chemistry revision.
1. Check the specification (syllabus) so that you know you have covered all the material.
2. Spend the last few days on the stuff that you don't know rather than just going over the stuff you do know.
3. Try some questions from the past papers. These are usually available from the exam board website or from your school or college.
4. It might not be much help now, but try to remember the bad feelings you are having now and use them to motivate you to greater and earlier efforts next time.
If you have specific questions, plese come back online and let me know. I will try to help you.
Thank you so much that really helps! It was a bit late for my mock but at least i can you use it for my real exam in the summer :D
However i was wondering if you could help me on everything to do with oxidation Numbers as my school didn't explain it that well?
Glad it was useful and sorry I am a bit late replying...I have been away a couple of days.
Oxidation numbers (sometimes called oxidation state)
You will have seen these in the past when you have seen "iron(III)chloride" or "copper (II) nitrate" on the labels of chemicals. The roman numerals refer to the oxidation number of the substance (iron or copper). You probably understand this as being the same as the "ion charge" on the metal ion (iron 3+, copper 2+).
It is sometimes useful to be able to think in terms of an "ion charge" for substances where they may not be an actual ion present. It is sometimes useful to be able to locate where the electrons are in a molecule. Oxidation number can help with this.
There are a series of rules for assigning oxidation number. Sorry there is no way round it but to learn them! The rules are hierarchical so rule 1 is more important than rule two etc.
1. All elements in their standard state have oxidation number of zero.
2. The total of all the oxidation numbers in a species (that means atom, molecule, ion etc) must add up to the overall charge on the species.
3. Fluorine is -1
4. Oxygen is -2 (except in peroxides when it is -1)
5. Hydrogen is +1 (except when it is a metal hydride, when it is -1)
What are the oxidation numbers of Na and F in NaF?
Total of oxidation numbers = zero (rule 2)
F = -1 (rule 3)
Therefore, Na = +1
What are the oxidation numbers of H and O in water?
O= -2(rule 4)
Therefore, H = +1
What are the oxidation numbers of O and F in F2O (sorry, can't do subscript)?
Therefore, O = +2 (even though rule 4 says oxygen should be -2, rules 2 and 3 are more important).
Hope this helps, if you need more, please get back online.
Copyright © 2007 - 2023 Revision World Networks Ltd.