10th Class Science Chemical Reactions and Equations Effect of Oxidation Reactions in Daily Life

          Effect of Oxidation Reactions in Daily Life

Many oxidation reactions take place in our daily life. Some of them are useful while others are harmful. The two such common oxidation reactions are:

• Corrosion

It is the degradation of metals due to their reaction with oxygen. Carbon-dioxide, water etc.

• Rusting

It is a common type of corrosion. It is formed when iron comes in contact with moist air. As a result of corrosion a reddish brown layer of ferric oxide is formed which is called is called rust.

\[4F{{e}_{(s)}}+3{{O}_{2(g)}}+2n{{H}_{2}}O\to 2F{{e}_{2}}{{O}_{3}}\cdot n{{H}_{2}}{{O}_{(S)}}\]  (Rust)

Copper articles when left out in moist air gets coated with a green layer. This is another example of corrosion where copper gets coated with basic copper carbonate layer.

\[2\,C{{u}_{(s)}}+C{{O}_{2}}_{(g)}+{{O}_{2}}_{(g)}\to CuC{{O}_{3}}\cdot Cu{{(OH)}_{2}}\]

• Effects of Corrosion

It weakens the metal and makes it brittle and reduces the tensile strength.  

           Methods of Preventing Corrosion

The spoiling of metals due to corrosion can be prevented by

• By coating the metal surface with oil, grease, paint, varnish
• By galvanizing i.e. coating the surface of iron objects with a thin layer of zinc.           
• By electroplating the metallic surface with less reactive metal.
• By alloying the various metals.

Do you know that corrosion can sometimes be advantageous. For e.g. Aluminium is a good conductor of electricity and is used in high tension wires. When it is exposed to air, it gets coated with a white protective layer of aluminium oxide \[(A{{l}_{2}}{{O}_{3}})\], this layer prevents the further corrosion of metal by moist air.

             Racidity

Often the food cooked is changed in taste if kept open for long, this is because the fats get oxidized an hence are degraded with time and start emitting bad smell.

The oxidation of oils and fats present in the foodstuff resulting into a bad odor and taste is called rancidity.

Methods to prevent rancidity:

• Antioxidants like BHA (Bitylated hydroxyl anisole) and BHI (Bitylated hydrolyzed) can be added to food stuff.
• Food should be kept in air tight container to prevent its oxidation.
• Nitrogen gas can be flushed while packing food stuffs like chips, namkeen etc.

         The process of coating iron with zinc is called:

(a) Electroplating

(b) Polishing

(c) Galvanization

(d) Reduction

(e) None of these

Answer: (c)

Explanation

Galvanization is the process of coating iron with zinc in order to prevent its rusting.

          Rancidity is due to:

(a) Reduction of oils and fats

(b) Oxidation of oils and fats

(c) Displacement of oil and fats

(d) Combination of oils and fats

(e) None of these

Answer: (b)

Explanation 

Oxidation of oils and fats present in food stuff is called rancidity.

           Identify the substance which is reduced in the given reaction below?

\[Pb{{S}_{(s)o}}+4{{H}_{2}}{{O}_{2}}_{(aq)}\to Pb\,S{{O}_{4}}_{(s)}+4{{H}_{2}}{{O}_{(e)}}\]

(a) Hydrogen peroxide

(b) Lead sulphide

(c) Both Lead sulphide and Hydrogen peroxide

(d) Water

(e) None of these

Answer: (a)

           Which one of the following is an example of displacement reaction?

(a) \[C{{l}_{2}}+2KBr\to 2KCl+B{{r}_{2}}\]

(b) \[2K+{{I}_{2}}\to 2Kl\]

(c) \[2{{H}_{2}}S+S{{O}_{2}}\to 2{{H}_{2}}O+3S\]

(d) \[CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}\]

(e) None of these

Answer: (a)

           Which one of the following is an example of addition reaction?

(a) \[C{{l}_{2}}+2KBr\to 2KCl+B{{r}_{2}}\]

(b) \[Fe+CuS{{O}_{4}}\to FeS{{O}_{4}}+Cu\]

(c) \[2{{H}_{2}}S+S{{O}_{2}}\to 2{{H}_{2}}O+3S\]

(d) \[CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}\]

(e) None of these

Answer: (d)

• Magnesium ignites easily and burns very brightly.
• When potassium chlorate is heated to melting point, any item added to it will cause a rapid disintegration in the form of an explosion.
• When a superconductor is cooled to below its transitional temperature, it becomes diamagnetic.
• Sodium acetate, when heated and cooled, becomes supersaturated in water.

• The universe is full of changes. The changes which take place around us are of two types. Physical changes and chemical changes.
• The chemical changes can be represented by means of chemical equation which involves all the formulas, states etc. of the reactants and products.
• A balanced chemical equation has equal number atoms of each elements on reactant and the product side. It always follows the law of conservation of mass.
• The chemical reactions taking place ground us are classified as: Combination reactions, displacement reaction, double displacement reactions, decomposition reaction and redox reaction.
• The chemical reactions are very useful in our day to day life and the oxidation reactions are taking place very frequently around us.
• Symbols used

(s): It represents the solid state

(I): It represents the liquid state

(g): It represents the gaseous state

(aq): Aqueous state i.e. solution in water

(ppt): Precipitate