Revision for test - Monday, 15th December

Just a reminder that our test will be in tomorrow's lesson, with questions on:
- Oxidation numbers and redox
- Intermolecular forces
- Group 7
- Group 2

You can find some revision resources at the following link, which I hope you will find useful.
http://cedarschemistry.edublogs.org/revision-resources-dec-2008/

See you on Monday!

Increasing reactivity of group 2

The reactivity of of group 2 increases as you go down, and the first ionisation energy decreases down to Barium, because of the increased atomic size and more shielding. However, the first ionisation energy of radium is slightly higher than barium, 509 kJ/mol compared to 502. Is this because the nucleus of radium is so much larger so counteracts the effect of another full shell of electrons?
Also, what chemical and physical properties of Group 2 do we have to know?

Mr Beaumont sheet

On the sheet Mr Beaumont gave us, Q13 is
Cr2O7 2- + 14 H+ + 6 e- ---> 2Cr3+ + 7H2O
Fe2+ ----> Fe3+ + e-
60 cm3 of acidified dichromate (VI) solution with a concentration of 0.05 mol/dm3 was titrated against a 0.6 mole/dm3 Fe 2+ solution. What volume of Fe 2+ solution would be required to reach the end point of this titration?

I don't understand how the equations above help you to work out what happens in the titration except for the fact you can see what the ions of each substance are...
Thanks.

halogens

halogens decrease in reactivity down the group, because their ability to gain electrons decreases because:
the atomic radi increases
the electron shielding increases
...
how excactly do these two factors affect its oxidising ability? is it because the electrostatic attraction between the electrons they may gain has decreased because of these two factors, or something completely different?

Work for Mrs Sudbery's group - 1st December

Sorry not to be in our lesson today but I hope to be back in by Wednesday. You should have been provided with work for the lesson but if not, please download it by following the link below and right-clicking on the document names.

http://cedarschemistry.edublogs.org/group-7-resources/