# Gravimetric Analysis

## What is Gravimetric Analysis?

Gravimetric analysis is a method in analytical chemistry to determine the quantity of analyte based on the mass of a solid. Example: Measuring the solids suspended in the water sample – Once a known volume of water is filtered, the collected solids are weighed.

#### The principle of Gravimetric Analysis:

The principle behind the gravimetric analysis is that the mass of an ion in a pure compound and can be determined. Later, used to find the mass percent of the same ion in a known quantity of an impure compound. ### Steps followed in the Gravimetric Analysis

1. Preparation of a solution containing a known weight of the sample.
2. Separation of the desired constituent.
3. Weighing the isolated constituent.
4. Computation of the amount of the particular constituent in the sample from the observed weight of the isolated substance.

### Types of Gravimetric Analysis

There are 4 fundamental types of gravimetric analysis. Of which, there are 2 common types involving changes in the phase of the analyte to separate it from the rest of a mixture, resulting in a change in mass.

#### Volatilization gravimetry

• Volatilization Gravimetry involves separating components of our mixture by heating or chemically decomposing the sample.

#### Precipitation gravimetry

• Precipitation Gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid.

#### Electrogravimetry

• Electrogravimetry is a method used to separate and quantify ions of a substance, usually a metal.

#### Thermogravimetric

• Thermogravimetric is a method of thermal analysis in which changes in physical and chemical properties of materials are measured as a function of increasing temperature or as a function of time.

### Advantages of Gravimetric Analysis

If the methods are followed carefully, it provides exceedingly precise analysis. It is used to determine the atomic masses of many elements to six-figure accuracy. It provides a little room for instrumental error and does not require a series of standards for calculation of an unknown.

### Disadvantages of Gravimetric Analysis

It usually provides only for the analysis of a single element, or a limited group of elements, at a time. Comparing modern dynamic flash combustion coupled with gas chromatography with traditional combustion analysis.

### Examples of Gravimetric Analysis

#### Question:

An ore is analyzed for the manganese content by converting the manganese to Mn3O4 and weighing it. If a 1.52g sample yields Mn3O4 weighing 0.126g, what would be the percent Mn3O3 in the sample? The percent of Mn?

#### Solution

%Mn2O3=0.125gMn3O4×3Mn2O32Mn3O4(gMn2O3/gMn3O41.52gsample×100%

=0.126g×[3(157.9)/2(228.8)]1.52g×100%=8.58%

%Mn=0.126gMn3O4×3MnMn3O4(gMn/gMn3O4)1.52gsample×100%

=0.126g×[3(54.94)/228.8]1.52g×100%=5.97%