The key difference between chlorine and chlorine dioxide is that the oxidation state of chlorine atom in chlorine or chlorine gas is zero whereas the oxidation state of chlorine atom in chlorine dioxide is +4. Further, the physical difference between chlorine and chlorine dioxide is that the chlorine is a pale yellow-green gas with a pungent, irritating odor while the chlorine dioxide is a yellow to reddish gas with an acrid odor.
Both chlorine and chlorine dioxide are gaseous compounds. They have different chemical and physical properties and thus, different applications. Since chlorine is a group 7 chemical element, the most common oxidation state of it is -1. However, the chlorine atom in chlorine dioxide has the +4 oxidation state.
CONTENTS
1. Overview and Key Difference
2. What is Chlorine
3. What is Chlorine Dioxide
4. Side by Side Comparison – Chlorine vs Chlorine Dioxide in Tabular Form
6. Summary
What is Chlorine?
Chlorine is a gaseous compound having the chemical formula Cl2. It is a pale yellow-green gas at room temperature and pressure. It acts as an extremely reactive agent, thus, is a strong oxidizing agent. Moreover, it has a pungent, irritating odor. This odor is similar to bleach. The IUPAC name of this gas is “molecular chlorine”.
Figure 01: Chlorine Gas Color
The molar mass of chlorine gas is 70.9 g/mol. The two chlorine atoms in this molecule are covalently bonded to each other. We call it a “diatomic gas” because there are two atoms linked to each other per one molecule. The inhalation of this gas is toxic and it is also an irritant to the eye. The gas is slightly soluble in water and can liquefy at -35◦C. However, we can readily liquefy this gas by applying an appropriate pressure at room temperature. Moreover, this gas is not flammable, but it can support the combustion.
More importantly, this gas is toxic if we inhale it. The chlorine gas is heavier than normal air. Thus it tends to collect at lower areas of the atmosphere. The melting and boiling points are -101°C and -35°C respectively. It is useful as a disinfectant in many industries, for water treatment, to make war gases, etc.
What is Chlorine Dioxide?
Chlorine dioxide is an inorganic compound having the chemical formula ClO2. It is a yellow to reddish gas. This gas crystallizes at −59 °C which appears as orange-coloured crystals. This is a common oxide of chlorine. The molar mass is 67.45 g/mol. It has an acrid odor. The melting and boiling points are −59 °C and 11 °C respectively. This is a neutral compound and is very different from elemental chlorine. It has a very high water solubility. Especially it can dissolve in cold water. The solubility is about 10 times higher than chlorine gas. Moreover, it does not hydrolyze when we dissolve it in water. Therefore, it remains as a dissolved gas in water. The oxidation state of chlorine atom in this molecule is +4. Since this molecule has an odd number of electrons, it is paramagnetic.
Figure 02: Liquefied Chlorine Dioxide
The major applications of this gas include in bleaching wood pulp, in elemental chlorine free bleaching purposes, drinking water treatments, as a fumigant treatment, etc.
What is the Difference Between Chlorine and Chlorine Dioxide?
Chlorine is a gaseous compound having the chemical formula Cl2. On the other hand, chlorine dioxide is an inorganic compound having the chemical formula ClO2. The melting and boiling points of chlorine gas are very low compared to chlorine dioxide. More importantly, chlorine dioxide is highly water soluble; it dissolves even in cold water. This solubility is about 10 times higher than that of chlorine gas. Both these compounds derive from chlorine element. The key difference between chlorine and chlorine dioxide is that the oxidation state of chlorine atom in chlorine gas is zero whereas the oxidation state of chlorine atom in chlorine dioxide is +4.
The below infographic presents more details on the difference between chlorine and chlorine dioxide in tabular form.
Summary – Chlorine vs Chlorine Dioxide
Chlorine and chlorine dioxide are gaseous compounds at room temperature and pressure. The difference between chlorine and chlorine dioxide is that the oxidation state of chlorine atom in chlorine gas is zero whereas the oxidation state of chlorine atom in chlorine dioxide is +4.
Reference:
1. “Chlorine.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here
2. “Chlorine Dioxide.” Wikipedia, Wikimedia Foundation, 22 Aug. 2018. Available here
Image Courtesy:
1.”Chlorine ampoule”By W. Oelen (CC BY-SA 3.0) via Commons Wikimedia
2.”Chlorine dioxide solution”Með Iridos – Own work, (Public Domain) via Commons Wikimedia