Question

In which of the following reactions can equilibrium be attained?
(a)Reversible reaction
(b)Irreversible reaction
(c)Redox Reaction
(d)Single Displacement reaction

Answer 1

Hint : In order to answer the question we need to understand what is a chemical reaction and what is Equilibrium. Chemical reaction is a process by which one or more substances called reactants are converted into products. The substance can be elements or atoms. Equilibrium is a state in which the rate of forward reaction becomes equal to the rate of backward reaction.

Complete Step By Step Answer:
Now first we need to understand all the given reaction types in detail.
Reversible Reaction-A reversible reaction is the one in which the reactants convert into product and product convert into reactants simultaneously. We take an example-
${H_2}_{(g)} + {I_{2(g)}} \rightleftharpoons 2H{I_{(g)}}$
In this case firstly hydrogen and iodine combine to form hydrogen iodide then after some time hydrogen iodide concentration increases and begins converting to hydrogen and iodine. There is a state reached when the rate of conversion of reactants to products becomes equal to the rate of conversion of products to reactants, this is called state of equilibrium. Thus equilibrium is hence achieved during reversible reaction.
Irreversible reaction-Irreversible Reactions are unidirectional reactions where reactants convert into products but not the vice versa. We take an example-
${C_x}{H_y} + {O_2} \to C{O_2} + {H_2}O$
Combustion reaction is an example of irreversible reaction because hydrocarbons convert into carbon dioxide and water but it cannot be converted back to the reactants. Hence we see irreversible reactions do not attain the state of equilibrium.
Redox Reaction-Redox reactions are those reactions in which electron transfer occurs between species. We take an example-
$Zn + C{u^{ + 2}} \to Z{n^{ + 2}} + Cu$
Redox reactions rarely observe equilibrium conditions.
Single displacement reaction-A reaction in which a single element is displaced by another element.
We take an example-
$Zn + CuC{l_2} \to ZnC{l_2} + Cu$
Hence these reactions also do not attain a state of equilibrium.
So the correct answer is option (a) Reversible Reaction.

Note :
The equilibrium is affected by several conditions like Concentration, temperature, pH etc.
One Example of reversible reaction in real life is binding of oxygen to Haemoglobin to form oxyhaemoglobin and then this is how we transfer oxygen to all parts of the body. However the binding of oxygen is affected by carbon dioxide concentration and pH.