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# A2 Chemistry Unit 5 IAL Edexcel Help!

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1. Hey guys! I have been stuck with these type of questions recently.. Could you please help me understand how to do number 2) c)? Thanks a lot!!
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2. (Original post by Sandy_Vega30)
Hey guys! I have been stuck with these type of questions recently.. Could you please help me understand how to do number 2) c)? Thanks a lot!!
A standard electrode potential is measured when you start with exactly 1 mole of chromium 3 in the solution. In chromium 3 sulphate, each molecule contains 2 chromium atoms, thus, each mole of chromium 3 sulphate molecules contains 2 moles of chromium atoms, but you only want 1 mole of chromium atoms, then how many moles of chromium 3 sulphate do you need? Well, half a mole. If the mass of a mole of chromium 3 sulphate is 300g or whatever, then how grams are there in half a mole of chromium 3 sulphate?
3. (Original post by oShahpo)
A standard electrode potential is measured when you start with exactly 1 mole of chromium 3 in the solution. In chromium 3 sulphate, each molecule contains 2 chromium atoms, thus, each mole of chromium 3 sulphate molecules contains 2 moles of chromium atoms, but you only want 1 mole of chromium atoms, then how many moles of chromium 3 sulphate do you need? Well, half a mole. If the mass of a mole of chromium 3 sulphate is 300g or whatever, then how grams are there in half a mole of chromium 3 sulphate?
Thanks a lot! But do we want only one mole of Chromium ions? What's the reason for that?
4. (Original post by Sandy_Vega30)
Thanks a lot! But do we want only one mole of Chromium ions? What's the reason for that?
Yea we do. The electrode potential of a cell varies with the concentration. The higher the concentration, the more they push (or pull) against the electrode and thus the electrode potential varies. Hence, chemists need to agree on a standard concentration to measure the potential difference with, it just so happens that 1 mol is the concentration they chose to be the standard.
5. (Original post by oShahpo)
Yea we do. The electrode potential of a cell varies with the concentration. The higher the concentration, the more they push (or pull) against the electrode and thus the electrode potential varies. Hence, chemists need to agree on a standard concentration to measure the potential difference with, it just so happens that 1 mol is the concentration they chose to be the standard.
Thanks a lot!! You are a life saver!!
6. (Original post by Sandy_Vega30)
Thanks a lot!! You are a life saver!!
Let me know if you have any more questions ^_^
7. (Original post by oShahpo)
Let me know if you have any more questions ^_^
Sure!

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