Question

In Permanganometric titrations, the end point is:
A.Yellow color
B.Pink color
C.Red color
D.Colorless

Answer 1

Hint: Permanganometric titrations are redox titrations in which Potassium permanganate is the oxidant and reductant.

Complete step by step answer:
A chemical reaction which involves both oxidation and reduction is known as Redox reaction. Oxidizing agents are titrated against reducing agents. Such titrations are known as Redox titrations.
Commonly we use Potassium permanganate, potassium dichromate and Cerium sulphate as oxidants.
We know that Potassium permanganate is a very strong oxidizing agent in acid medium. It will easily reduce to colorless Mn2+ ions. The reaction is given by the equation
$$Mn{O_4}^{-}+8H^{+}+5e^{-}$$ $$\to$$ $$M{n}^{2+}+4H_{2}O$$
This reaction has a very high reduction potential value
 $$E_0$$ = 1.51 V
This high value of reduction potential indicates that $$MnO4-$$ has a high tendency to undergo reduction to Mn2+ and it acts as a strong oxidant.
When we titrate a definite volume of colorless solution of a reducing agent against permanganate, the use of indicator is unnecessary. Because Potassium permanganate has a pink color. It imparts color to the solution. So, the appearance of permanent pale pink color towards the end of titration shows the end point. Thus, potassium permanganate itself acts as a self-indicating agent.
Eg: Oxalic acid can be titrated against Potassium permanganate.
$$2KMn{O}_4+3H_{2}S{O}_4+5H_2{C}_2{O}_4$$ $$\to$$ $$K_{2}S{O}_4+2MnS{O}_4+8H_{2}O+10C{O}_2$$
Hence, the correct answer is option (B) i.e Pink Color.

Note: Normally we add KMnO4 from the burette to the reducing agent containing dilute $$H_{2}S{O}_4$$ in a conical flask. We use only dilute $$H_{2}S{O}_4$$ for introducing acidity. Other acids like Con. $$H_{2}S{O}_4$$ and Con. $$HN{O}_3$$ may interfere in the reaction of permanganate with the reductant. Potassium permanganate is not a primary standard. It is contaminated with a small amount of $$Mn{O}_2$$ . So, we standardize it using oxalic acid or Mohr salt.