redox equilibria

If you need some answers for the predicting redox reactions worksheet you have used in class you can find them here.

predicting redox reactions worksheet

predicting redox reactions answers

nitrogen triiodide

Strike day, and a bit of free time to play around with some home made explosives.

Nitrogen triiodide is worryingly easy to make, and extremely unstable. It is a contact explosive when dry, and produces a beautiful plume of iodine vapour mixed with nitrogen gas when detonated.



As you can see and hear from the video, the explosion is fairly impressive given the small quantity used. You can see that the metre ruler suffers for its art, and you may just be able to make out Mr Chivers' exclamation from his nearby office just as it goes off.

Anyone interested in why it's so unstable will need to consider the entropy change for the reaction.

2 NI₃ (s) → N₂ (g) + 3 I₂ (g)

The large increase in the number of moles from left to right, in addition to the production of gases from a solid, leads to an enormous increase in entropy. Also, the reaction is clearly exothermic. These two factors are ideal for giving a negative free energy change for the reaction, indicating a highly likely, spontaneous reaction.

CHEM5 papers

If you scroll down this post a bit you'll find some papers and mark schemes for your revision, although hopefully you'll have had many of the answers fully explained in class by now. Just remember that there are some synoptic elements to CHEM5, meaning that the board can ask you anything from earlier modules which have a link to the new content studied in module 5.

As far as I can see, the most likely subject areas to crop up again are:

Thermodynamics
· Calorimetry (from CHEM2)
· Equilibria and Le Chatelier (CHEM2)

Redox Equilibria and cells
· Redox behaviour of halogens (CHEM2)

Periodicity
· Physical trends in period 3, melting point, 1st ionization energy etc. (CHEM1)
· Solubility trends of sulphates/hydroxides (CHEM1)
· Extraction of aluminium (CHEM2)

Transition Metals
· Electron configuration (CHEM1)
· Shapes of molecules (CHEM1)
· Extraction of metals, iron, aluminium, titanium (CHEM2)

At any point they could very easily throw in a pV=nRT calculation as well, so make sure you know the standard units.

CHEM5 2010 written paper

CHEM5 2010 mark scheme

Specimen written paper

Specimen mark scheme

Older CHM5 papers can be found further down. Just be careful to ignore any organic chemistry or other module 4 based questions on the old syllabus papers. However, if you are resitting the CHEM4 paper then there will be some useful stuff on here for you to try on equilibria and acid calculations, as well as the essential organic stuff.

If you need any more old CHM5 papers then send me a quick email and I'll let see what I can do.

CHM5 2008 written paper (old syllabus)

CHM5 2008 mark scheme (old syllabus)

CHM5 2009 written paper (old syllabus)

CHM5 2009 mark scheme (old syllabus)

Sorry, I don't have an electronic copy of the written paper, but,
CHM5 2010 mark scheme (old syllabus)

Make sure you come in if you need any help.

electrode potentials answers

We've been working on predicting reactions using electrode potentials in class and here are the answers to the worksheet we started.

predicting redox reactions

year 13 born haber worksheet

You may have been given a worksheet in class with several Born Haber cycle questions for you to have a go at. Here you can download a powerpoint with the correct answers for you to check through as part of your revision.

born haber powerpoint answers


Mr Born and Mr Haber in happier days before the split

calorimetry

Calorimety calculations come up pretty often on your CHEM2 paper, and any Year 13 students might also expect them as synoptic content on CHEM5.

The powerpoint you can download from the link below will remind you of the basics and give you worked examples for a number of calculations.

calorimetry worksheet answers

transition metal reactions

Year 13 powerpoint stuff for transition metals. It's pretty good but I'll let you decide if it's better than my technicolour sheet (how can it be?)

reactions of transition metals

born haber cycles

Ahh, the boundless joy of Born Haber cycles. If they're sending you round in circles then try these resources.

Download a powerpoint to help your understanding
NaCl Born Haber

Build your own cycle with this exercise
NaCl drag and drop