A solution of potassium permanganate (KMnO4) was standardised by titrating with 0.1908 g of Na2C2O4 dissolved in 50 cm3 of acidified water. The endpoint was reached after 24.50 cm3 of solution had been added. Calculate the molar concentration of KMnO4 in the solution.
I worked a problem just like this last night. Post your work if you run into trouble.
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To calculate the molar concentration of KMnO4 in the solution, we need to use the balanced equation and mole ratios from the titration.
1. First, let's write the balanced equation for the reaction between KMnO4 and Na2C2O4:
2 KMnO4 + 5 Na2C2O4 + 8 H2SO4 → 2 MnSO4 + 10 CO2 + 8 H2O + 5 Na2SO4
This balanced equation tells us that 2 moles of KMnO4 react with 5 moles of Na2C2O4.
2. Next, let's calculate the number of moles of Na2C2O4 used in the titration:
Mass of Na2C2O4 = 0.1908 g
Molar mass of Na2C2O4 = 2(22.99 g/mol) + 2(12.01 g/mol) + 4(16.00 g/mol) = 134.00 g/mol
Moles of Na2C2O4 = Mass of Na2C2O4 / Molar mass of Na2C2O4
= 0.1908 g / 134.00 g/mol
3. Now, let's convert the volume of KMnO4 solution used in the titration to moles:
Volume of KMnO4 solution = 24.50 cm3 = 0.0245 L
Moles of KMnO4 = Volume of KMnO4 solution × Molar concentration of KMnO4
4. Finally, calculate the molar concentration of KMnO4:
Molar concentration of KMnO4 = Moles of KMnO4 / Volume of KMnO4 solution
By following these steps, you should be able to calculate the molar concentration of KMnO4 in the solution.