Question

\[4{H^ + } + Mn{O_4}^{2 - } + {C_2}{0_4} \to M{n^{2 + }} + 2C{O_2} + 4O{H^ - }\]
For the proceeding reaction, which of the following statements is not always true based on the knowledge that oxalate reacts slowly at room temperature causing a fade in the purple colour due to the manganate ion?
A. Using an acid-base catalyst will increase the overall rate of the reaction.
B. There are multiple steps in the reaction mechanism.
C. The reaction is carried out at elevated temperature to make the procedure practical in terms of time.
D. Use of spectrophotometer and a Beer’s Law plot help determine the rate for the overall reaction mechanism.

Answer 1

Hint:
This reaction between oxalic acid and potassium permanganate occurs in acidic medium, as permanganate ion is a powerful oxidizing agent in an acidic medium.KMnO4 acts as an indicator as the permanganate ions are deep purple color. Use option elimination to tackle these types of questions.

Complete Step By Step Solution:
- When this reaction is complete there are so many steps you will notice so there are multiple steps in the reaction mechanism. Hence option B is correct.
- This reaction cannot be completed at constant temperature so elevated temperature is required to complete the reaction or procedure practical in terms of time. Hence option C is correct.
- And spectrophotometer and Beer’s law plot helps us to determine the rate of reaction so option C is also correct.
- Let’s move to option A. Acid-base catalyst is not always used to increase the rate of overall reaction. It is used to increase the rate of single side reactions. So option A is false.
Therefore, Incorrect option is A.

Additional Information:
Let’s know about spectrophotometer and Beer’s Law. The Beer-Lambert law also known as Beer’s law states that there is a linear relationship between the concentration and the absorbance of the solution. It helps us to calculate the concentration of solution by measuring how much it absorbed. A spectrophotometer helps us to find the amount of light passed through the solution.

Note:
Try to use option elimination methods in these types of questions. Also remember that acid-base catalysts increase the rate but only for singly sided reactions not always for overall reaction. Also read the question carefully asked for the incorrect option. Mostly students lose marks here.