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The concentration of Fe2+ in a solution is determined by titrating it with a 0.1956 M permanganate solution. The balanced net ionic equation for the reaction is: MnO4-(aq) + 5Fe2+(aq) + 8H3O+(aq) Mn2+(aq) + 5Fe3+(aq) + 12H2O(l) In one experiment, 20.81 mL of the 0.1956-M permanganate solution is required to react completely with 40.00 mL of the Fe2+ solution. Calculate the concentration of the Fe2+ solution.

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Answer:

The concentration of the Fe2+ solution is 0,508 M

Explanation:

MnO4-(aq) + 5Fe2+(aq) + 8H3O+(aq) → Mn2+(aq) + 5Fe3+(aq) + 12H2O(l)

My concentration of permanganate is 0,1956 M (moles of solute in 1L of solution) but I use, just 20,81 ml so I need to get those moles.

1000 mL ___ 0,1956 moles

20,81 mL ___ (20,81 . 0,1956) /1000 = 4,07x10*-3 moles

The ionic equation says that 1 mol of MnO4- reacts with 5 moles of Fe2+ so my 4,07x10*-3 moles are going to react wih (4,07x10*-3 . 5) = 0,020moles of Fe2+

This quantity of moles are in the solution required, in the volume i was given (40mL). To get the concentration I have to calculate the moles in 1L (MOLARITY)

40mL ___ 0,020 moles of Fe2+

1000 mL ___ (1000 . 0,020) /40 = 0,508 M

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