Key Difference – Qualitative vs Quantitative Analysis in Chemistry
 

Qualitative and quantitative analysis in chemistry are the major types of analytical techniques used in chemistry to determine the chemical composition of sample qualitatively and quantitatively. The key difference between qualitative and quantitative analysis in chemistry is that qualitative analysis in chemistry gives the presence or absence of different chemical components in a sample whereas quantitative analysis in chemistry gives the amount of different chemical components present in a given sample.

CONTENTS

1. Overview and Key Difference
2. What is Qualitative Analysis in Chemistry
3. What is Quantitative Analysis in Chemistry
4. Similarities Between Qualitative and Quantitative Analysis in Chemistry
5. Side by Side Comparison – Qualitative vs Quantitative Analysis in Chemistry in Tabular Form
6. Summary

What is Qualitative Analysis in Chemistry?

Qualitative analysis in chemistry is a branch of chemistry that analyses the chemical composition of a sample. It indicates different elements, or groups of elements such as functional groups, etc. present in the sample. Therefore, a qualitative analysis of a sample can be used to determine whether a particular component is present in a sample or not. However, this analysis does not provide any information about the quantity of that chemical component. The qualities in the sample that are often considered in the analysis are colour, odour, melting point, boiling point, reactivity, precipitation, etc.

The qualitative analysis is found in two types; organic qualitative analysis and inorganic qualitative analysis. Among them, the organic qualitative analysis determines the functional groups and chemical bonds in the sample whereas inorganic qualitative analysis, most of the times, determines the ions present in the sample.

The chemical techniques used in the qualitative analysis of a sample can include the followings;

Examples of Qualitative Analysis in Chemistry

Let us consider a couple of examples to understand the qualitative analysis of a sample.

• Iodine Test (An Organic Qualitative Analysis Technique)

The iodine test is used to indicate the presence or absence of starch. It is sugar, which is an organic compound. There, liquid iodine is used as the indicator. A spot test can be used to test (Take a white tile and put some drops of the samples that are going to be analyzed. Then add iodine solution to each drop of sample. If the colour of the sample is changed to a brown colour, it indicates the presence of starch).

• Flame Test (An Inorganic Qualitative Analysis Technique)

Figure 01: Zinc Flame Test

In the flame test, the presence of a certain metal or its ions can be determined. Different metal atoms give different colors to the flame. According to the flame color given when a portion of the sample is burnt in the Bunsen burner, can determine the presence of some metal ions. Ex: Zinc gives a green flame color.

What is Quantitative Analysis in Chemistry?

Quantitative analysis in chemistry is a branch of chemistry that deals with the quantities of different components in a sample. The quantity can be given as a mass, volume, concentration, relative abundance, etc. There are chemical or physical methods that are used in the quantitative analysis.

Chemical Methods

Chemical methods include chemical reactions (ex: oxidation, reduction, precipitation, neutralization, etc.), titration methods, gravimetric methods, combustion analysis techniques, etc.

Physical Methods

Physical methods analyses one or more physical properties of a sample. Some examples include AES (Atomic emission spectroscopy), x-ray fluorescence spectroscopy, mass spectroscopy, etc.

But most of the times, physical and chemical analysis techniques are used together with some calculations to determine the exact amount of a component in a given sample. However, there can be many interferences and experimental errors that cause faulty final results.

Figure 02: Titration Methods

Quantitative analysis of a sample is very important for several reasons. It gives the details about how much reactant should be used to perform a chemical synthesis reaction to get a certain amount of product, hence the waste of chemicals is reduced (atom economy is increased), it can be used to determine the quality of food or any other product by indicating the presence of appropriate amounts of ingredients, it is helpful in determining the purity if a sample, etc.

What are the Similarities Between Qualitative and Quantitative Analysis in Chemistry?

• Both Qualitative and Quantitative Analysis in Chemistry are analytical techniques.
• Both Qualitative and Quantitative Analysis in Chemistry techniques give details about the components in a sample.
• Most of the times, these techniques are used together (Ex: use qualitative analysis followed by quantitative analysis)

What is the Difference Between Qualitative and Quantitative Analysis in Chemistry?

Summary – Qualitative vs Quantitative Analysis in Chemistry

Qualitative and quantitative analysis in chemistry gives the details of a given sample such as chemical composition and the amounts of different components present in that sample. The difference between qualitative and quantitative analysis in chemistry is that the qualitative analysis in chemistry gives the presence or absence of different chemical components in a sample whereas quantitative analysis in chemistry gives the amount of different chemical components present in a given sample.

Reference:

1.Helmenstine, Anne Marie, D. “Qualitative Analysis Definition (Chemistry).” ThoughtCo, Oct. 17, 2017. Available here 
2.The Editors of Encyclopædia Britannica. “Qualitative chemical analysis.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 27 July 2012. Available here  
3.Helmenstine, Anne Marie, D. “Understanding Quantitative Analysis in Chemistry.” ThoughtCo, Feb. 12, 2017. Available here  

Image Courtesy:

1.’Zinc flame test’By Chemicalinterest – Own work, (Public Domain) via Commons Wikimedia  
2.’ChemicalPrinciplesFig2-3’By Dickerson, Gray and Haight (CC BY 3.0) via Commons Wikimedia 

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