Question

Which of the following steps are not involved in gravimetric analysis:

• A. Precipitation
• B. Indicator
• C. Digestion
• D. Filtration

Hint:

In gravimetric analysis, focus on the techniques that involve separating and weighing the precipitate, such as precipitation, digestion, and filtration.

Answer 1

The Correct Option is B

Gravimetric analysis involves precipitation, digestion, and filtration as key steps. The process does not require the use of an indicator, as it relies on the mass of the precipitate for analysis rather than any visual change that would require an indicator.

Answer 2

Gravimetric analysis is a quantitative method that determines the amount of a substance by measuring the mass of a solid product formed from it, so it helps to walk through what its actual workflow looks like:

1. Precipitation: The analysis starts by adding a reagent that reacts with the analyte to form an insoluble solid, the precipitate. This step is central to gravimetric analysis, since the whole method depends on generating a solid that can later be weighed.
2. Indicator: An indicator is a substance that changes colour to signal the endpoint of a reaction, and it is a defining feature of titrimetric or volumetric analysis, where a colour change tells you when to stop adding titrant. Gravimetric analysis does not rely on any colour change at all, since the answer comes from a measured mass, not a visual endpoint, so this step does not belong here.
3. Digestion: After precipitation, the mixture is often warmed and left to stand so that small, impure crystals can grow into larger, purer, more easily filtered particles. This digestion step is a standard part of gravimetric procedure, improving the quality of the final precipitate.
4. Filtration: Once the precipitate has matured, it is separated from the liquid by filtration, then washed to remove impurities before it is dried or ignited and weighed. Filtration is an essential mechanical step in every gravimetric procedure.

Three of these four steps, precipitation, digestion, and filtration, are all part of building and isolating a solid precipitate whose mass gives the answer. An indicator has no such role, since gravimetric analysis never relies on a visual colour change to determine the result.

So the correct answer is Indicator.