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1. Hi any help is appreciated

A mixture of magnesium chloride and magnesium sulphate is known to contain 0.6mol of chloride ions and 0.2 mol of sulphate ions.

What is the number of moles of magnesium ions present?
A 0.4
B 0.5
C 0.8
D 1.0

This question is from SQA past paper 2006

Thanks
2. well, the formula of magnesium chloride is MgCl2 and magnesium sulphate is MgSO4

Your 0.6mol of chloride ions, must have come from the MgCl2 and the 0.2 mol of sulphate ions must have come from the MgSO4

So how many moles of Mg2+ do you have?
3. I dont know, the answer is B 0.5 but I dont know how to get to 0.5
4. well, if you have 0.6 mol of chloride ions, and each MgCl2 produces two chlorides, you must have 0.3 mol of MgCl2 - agreed?

And if you have 0.2 mol of sulphate ions, and each MgSO4 produces one sulphate, then you must have 0.2mol of MgSO4 - agreed?

Now, each mole of MgCl2 produces one mole of Mg and each mole of MgSO4 produces one mole of Mg, so in total you will have 0.3 + 0.2 moles of Mg = 0.5 moles

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