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Quantitative analysis (chemistry)

physical science Maturity 9-11 Next article →

Scientists want to know exactly how much of a substance is in a mix. This task is called quantitative analysis. It helps them find the amount of one or more parts in a sample. They often use a percentage to show this amount.

Knowing this amount helps them learn about the properties of the sample. It is a very important part of analytical chemistry.

There are two main ways this work happens. One way is called gravimetric analysis. This method uses weight to find the amount of a substance. It gives very accurate data about a sample. However, it takes a lot of time to do in a lab.

Another way is called volumetric analysis. This method uses liquids to find the amount. It is faster than the first way. It can still give very good results.

Volumetric analysis often uses a process called titration. One type is a neutralization reaction. This happens when an acid and a base react together. This reaction creates salt and water.

Another type is a precipitation reaction. In this way, a liquid reacts to form a solid that does not dissolve. Scientists sometimes call this argentometry. They often use silver nitrate as a reagent for this.

Other special titrations exist for different jobs. Complex forming titration happens between metal ions and a liquid called EDTA. This name stands for Ethylene Diamine Tetra Acetic acid. There is also redox titration. This happens between an oxidizing agent and a reduction agent.

For organic compounds, scientists use methods like the Kjeldahl or Dumas methods. They might also use the Carius or Liebig methods. These names help scientists know which tool to use.

Quantitative analysis is different from qualitative analysis. Qualitative analysis asks what kind of substance is present. For example, a chemist might use NMR or IR spectroscopy to find an identity. Then, they use quantitative tools to find the amount.

Mass spectrometry can even look at proteins in biological samples. This can help find diseases like cancer. An indicator solution can also be used for both jobs. It might change color to show a substance is there. Or, scientists study the color to find the exact concentration.

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