Question

All the following about back nitration are true, EXCEPT

• A. It is performed when the rate of reaction between the analyte and reagent is fast
• B. It is performed when the rate of reaction between the analyte and reagent is slow
• C. It is performed when the standard lacks stability
• D. It is the process in which excess of standard solution used to react with an analyte is determined by titration with a second standard solution

Answer 1

The Correct Option is A

To address the question of back titration and determine which statement is not true, let's explore the concept and application of back titration. Back titration, also known as indirect titration, is a technique used in quantitative chemical analysis.

Here are the situations where back titration is typically used: 

1. When the rate of reaction between the analyte and reagent is slow: In such cases, it's more efficient to add an excess of a known standard solution and then titrate the unreacted excess with another standard solution.
2. When the standard solution lacks stability: It might be impractical to perform a direct titration if the solution degrades or reacts slowly.
3. It involves the process in which an excess of a standard solution is reacted with an analyte, and the leftover (unreacted) portion is titrated with a second standard solution to determine the amount initially reacted.

Given the options:

It is performed when the rate of reaction between the analyte and reagent is fast

• — This is usually not a reason for performing back titration, because if the reaction is fast, direct titration would be preferable.

It is performed when the rate of reaction between the analyte and reagent is slow

• — This is a valid reason to use back titration.

It is performed when the standard lacks stability

• — This is also a valid scenario for back titration.

It is the process in which excess of standard solution used to react with an analyte is determined by titration with a second standard solution

• — This describes the process of back titration accurately.

Based on the explanations above, the statement "

It is performed when the rate of reaction between the analyte and reagent is fast

" is not true for back titration, as this method is typically reserved for cases where the direct reaction is not feasible due to slow reaction rates, instability, or other similar issues.