posted by amy on .
A solution of ferrous sulfate (FeSO4) is titrated with a solution of potassium permanganate in sulfuric acid. The balanced half reactions are as follows:
10FeSO4 + 5 H2SO4 --> 5 Fe2(SO4)3 + 10 H ^+ +10e^-
and 2 KMnO4 + # H2SO4 +10e^- --> 2 MnO4 + K2SO4 + 8 H2O.
The gram-formula mass of FeSO4 is 151.91 g/mol, and that of KMnO4 is 158.04 g/mol.
1. What is the gram-equavalent mass of FeSo4 for this reaction?
2. What is the gram-equavalent mass of KMnO4 for this reaction?
3. If 5.35 g of KMnO4 are dissolved in a liter of solution, what is the normality of the solution?
4. If 65.34 mL of 0.1000 N KMnO4 are required to titrate 45.28 mL of FeSO4 solution, what is the normality of the solution?
5. Carbon monoxide is detected in air samples by its reaction with diiodine pentoxide to form carbon dioxide and elemental iodine: CO + I2O5 --> CO2 + I2. Balance the equation.
These questions really scare me!!! I have just started this new chapter in my chemistry lessons and I don't get it at all!!!PLEASE HELP!!
You need to re-read the chemistry book chapter(s). I'm not sure I buy the equations you have written; the first one shows Fe changing from +2 to +3, which is OK, but the second one shows no change in Mn. It should change from +7 on the left to +2 on the right and a more likely product is MnSO4 rather than MnO4. The second point is to remember in these reactions that
equivalent mass = molar mass/delta e per mole. For FeSO4 that is molar mass/1. For KMnO4 that is molar mass/5.
For #3, normality = # equivalents/liter of solution.
For #4, use mL x N = mL x N
For #5, this is a standard redox equation to balance; redox equations are balanced following rules. Here is a site that give some simple rules.