Question

Write the chemical properties of Oxygen.

Answer 1

Chemical properties of Oxygen

Oxygen is a chemically active gas. It reacts directly with nearly all elements except for inert gases and halogens.

(I) Action of litmus

• Oxygen combine with metal to form basic oxide whereas it combines with nonmetals to form acidic oxide.
• We can observe the nature of a solution using litmus paper which is an indicator.
• Blue litmus changes to red in acidic solution and red litmus changes to blue in alkaline solution.
• There is no change in the colour of litmus paper in neutral solution.
• When moist blue and red litmus papers are lowered into a jar containing pure oxygen, then no change in colour of both the litmus papers is observed. This shows that oxygen is neutral.

(II) Combustibility

• Oxygen does not burn but supports combustion.
• Combustion also commonly known as burning is a chemical reaction in which a substance reacts rapidly with oxygen to produce heat and light.
• The combustion of fuels like petrol and diesel is an example of burning.
• It has been observed that certain substances have to be heated to a certain temperature before they start burning.
• The lowest temperature to which a substance must be heated before it begins to burn is called its ignition temperature.

(III) Reactivity

• Oxygen reacts with metals and non-metals to form new compounds called oxides.
• The process of formation of these oxides is called oxidation.
• When an element burns in oxygen, the reaction is called an oxidation reaction or simply oxidation. Such a reaction involves the addition of oxygen to form oxide.
• Combustion is an example of oxidation.
• Oxidation can be of different types based on the rate at which different substances combine.

Spontaneous oxidation

• When a substance without being ignited by a spark begins to burn on its own, it is called spontaneous oxidation.

$$\begin{gathered} 4\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right) \\ \mathrm{Sodium}\mathrm{Oxygen}\mathrm{Sodium}\mathrm{oxide} \end{gathered}$$

Rapid oxidation

• When a substance reacts with oxygen rapidly to release a large amount of heat and light energy, it is called rapid oxidation.

$$\begin{gathered} {\mathrm{CH}}_4\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{heat}+\mathrm{light} \\ \mathrm{Methane}\mathrm{Oxygen}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Water} \end{gathered}$$

Slow oxidation

• When a substance reacts with oxygen at a very slow rate, it is called slow oxidation.

$$\begin{gathered} 4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right) \\ \mathrm{Iron}\mathrm{Oxygen}\mathrm{Iron}\left(\mathrm{III}\right)\mathrm{oxide} \end{gathered}$$

(IV) Reaction of metals with oxygen

• Metals like sodium, calcium and magnesium burn in oxygen to produce their respective oxides.
• Heat is released in this process.

$$\begin{gathered} 4\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right) \\ \mathrm{Sodium}\mathrm{Oxygen}\mathrm{Sodium}\mathrm{oxide} \end{gathered}$$

(V) Reaction of non-metals with oxygen

• Non-metals like carbon, sulphur and phosphorous burn in oxygen to produce their respective oxides which are acidic.
• Heat is released in this process.

$$\begin{gathered} \mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{heat} \\ \mathrm{Carbon}\mathrm{Oxygen}\mathrm{Carbon}\mathrm{dioxide} \end{gathered}$$

(VI) Respiration

• The process in which oxygen reacts with the digested food to form carbon dioxide, water vapour and energy is called respiration.