Strength of oxalic acid is M/40 calculate readings of burette on taking 20ml of sodium hydroxide
Answers
Explanation:
Objective
Our objective is to determine the strength of KMnO4 solution by titrating it against a standard solution of;
Oxalic acid
Ferrous ammonium sulphate (Mohr’s salt)
The Theory
What is Titration?
Titration is a common laboratory method of qualitative chemical analysis that can be used to determine the unknown concentration of a solution (analyte). The basis of this process is the reaction between the analyte and a solution of unknown concentration (standard solution). The analyte is taken in a conical flask using a pipette and the solution of known concentration is taken in a calibrated burette (titrant).
Some Important Terms in Titration
1. Standard solution
A solution whose concentration is known, is called a standard solution. The substance used to prepare a standard solution is called the primary standard. Oxalic acid and sodium carbonate are some examples.
2. Concentration of a solution
Concentration of a solution is defined as the amount of a solute present in a definite volume of the solvent. Concentration of a solution can be expressed in different ways.
Titration of KMnO4 against Oxalic acid
Preparation of standard solution of Oxalic acid [250 ml M/10 (0.1 M) solution]
The molecular mass of crystalline oxalic acid is, H2C2O4.2H2O = 126
Weight of oxalic acid crystals required to prepare 1000 ml of 1 M solution = 126 g
Therefore, weight of oxalic acid required to prepare 250 ml 0.1
Determination of strength of KMnO4 using standard solution of oxalic acid
In this titration KMnO4 is the titrant and oxalic acid is the analyte. Here, potassium permanganate is the oxidizing agent and oxalic acid is the 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
No other indicators are used to determine the endpoint, because KMnO4 acts as the indicator. Permanganate (MnO4-) ion has a dark purple colour. In an acidic medium, MnO4- is reduced to colourless manganous (Mn2+) ions. On reaching the end point, the addition of the last single drop of permanganate imparts a light pink colour to the solution. The chemical reaction that takes place during titration can be represented by the chemical equation.
Balanced chemical equation
From the balanced chemical equation, it is clear that 2 moles of KMnO4 reacts with 5 moles of oxalic acid