To standardise a KMnO4 solution, 0.335 g of pure sodium oxalate, Na2C2O4 (molar mass 134), is dissolved in dilute H2SO4 and titrated hot, needing 41.7 mL of the permanganate solution. Find the molarity of the KMnO4 solution, to three decimal places.

JEE Main levelNumerical answerDifficulty 2 of 3rx188

To standardise a $KMnO X_{4}$ solution, 0.335 g of pure sodium oxalate, $Na X_{2} C X_{2} O X_{4}$ (molar mass 134), is dissolved in dilute $H X_{2} SO X_{4}$ and titrated hot, needing 41.7 mL of the permanganate solution. Find the molarity of the $KMnO X_{4}$ solution, to three decimal places.

Numerical answer type, answer in M, tolerance 0.0005.

mmol oxalate = 0.335/134 x 1000 = 2.50. From

2 MnO X_{4} X^{-} + 5 C X_{2} O X_{4} X^{2 -}

, mmol

MnO X_{4} X^{-}

= 2.50 x 2/5 = 1.00. Molarity = 1.00/41.7 = 0.0240 M.