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Q. 40 mL of `KMnO_4` is required in acidic medium to oxidise 0.280 g of `Na_2C_2O_4`...

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user8235304 | Student, Grade 11 | Valedictorian

Posted July 14, 2013 at 5:50 PM via web

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Q. 40 mL of `KMnO_4` is required in acidic medium to oxidise 0.280 g of `Na_2C_2O_4` (99.8% pure).What is the molarity of `KMnO_4` solution?

A) 0.0208 M

B) 0.104 M

C) 0.04 M

D) None of the above

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted July 14, 2013 at 6:09 PM (Answer #1)

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40 ml of `KMnO_4` is required to oxidize 0.280 g of `Na_2C_2O_4` . When the two solutions are mixed the reaction that takes place is `C_2O_4 + MnO_4 -> 2CO_2 + MnO_2 + O_2` . The `K^+` and `Na^+` ions react with the cations from the acid to form salts.

From the equation provided one mole of `C_2O_4` and one mole of `MnO_4` react with each other.

The molar mass of `Na_2C_2O_4` is 134,  0.280 g of `Na_2C_2O_4` is equivalent to `7/3350` moles. As this reacts with `MnO_4` present in 40 ml of `KMnO_4` , the molarity of the `KMnO_4` solution is `7/134 ~~ 0.0522`

The correct answer is option D.

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