Chemistry, asked by Ruchisingh1234, 1 year ago

prepare M/20 solution of oxalic acid with the help of the solution determine the molirity of given KMnO4 solution

Answers

Answered by abhi178
76

preparation of standard solution of oxalic acid [ 250ml / M/20 ] 

we know, molar mass of oxalic acid , H_2C_2O_4.2H_2O = 126g/mol 

given, molarity = 0.05M

and volume of solution , V = 250ml

so, mass of oxalic acid = M × molarity × V/1000

= 126 × 0.05 × 250/1000 

= 126 × 0.05/4 

= 1.575 g 

now, determination of strength of KMnO_4 using standard solution of oxalic acid. 

in this titration, potassium permanganate is titrant while oxalic acid is analyte. also we observed that potassium permanganate is oxidising agent. and oxalic acid is reducing agent.The reaction between potassium permanganate and oxalic acid is carried out in an acidic medium because permanganate ion in the acidic medium is a very strong oxidizing agent. Acidity is introduced by adding dilute sulphuric acid.

MnO_4^{2-}+8H^++5e^-\rightarrow Mn^{2+}+4H_2O

The chemical reaction that takes place during titration can be represented by the chemical equation.

molecular reaction, 

2KMnO_4+3H_2SO_4\rightarrow K_2SO_4+2MnSO_4+3H_2O+5[O]

H_2C_2O_4.2H_2O+[O]\rightarrow 2CO_2+3H_2O]\times5

--------------------------------------------------------

2KMnO_4+3H_2SO_4+5H_2C_2O_4.2H_2O\rightarrow K_2SO_4+2MnSO_4+18H_2O+10CO_2 is overall reaction. 

ionic reaction, 

MnO_4^{2-}+8H^++5e^-\rightarrow Mn^{2+}+4H_2O]\times2

C_2O_4^{2-}\rightarrow2CO_2+2e^-]\times5

---------------------------------------------------------------

2MnO_4^{2-}+5C_2O_4^{2-}+16H^+\rightarrow 2Mn^{2+}+8H_2O+10CO_2 overall ionic redox reaction. 

from balance chemical equation, it is clear that two mole of potassium permanganate reacts with five moles of oxalic acid. 

according to molarity concepts , 

molarity of KMnO_4 × volume of KMnO_4 /molarity of oxalic acid × volume of oxalic acid = mole of KMnO_4/mole of oxalic acid = 2/5 

so, molarity of KMnO_4 = molarity of oxalic acid × volume of oxalic acid × 2/volume of KMnO_4 × 5

If oxalic acid is to be titrated, add the required amount of dil. sulphuric acid and heat the flask to 60°-70°C. The purpose of heating is to increase the rate of reaction, which otherwise is slow at room temperature.


rishilaugh: thanks
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