Chemical Equilibrium mcqs

Chemical Equilibrium Important Multiple Choice Questions with Answers

Learning objectives : 

1.Define chemical equilibrium and discuss how it relates to reaction rates
2.For any reaction, write the expression for the equilibrium constant.
3.Convert Kc to Kp and vice versa conversion
4.Relate the relative proportions of reactants and products in an equilibrium mixture to the size of an equilibrium constant.
5.Adjust the equilibrium constant to account for modifications to the chemical equation
6.Create the expression for a heterogeneous reaction’s equilibrium constant.
7.Using concentration measurements, determine the equilibrium constant.
8.Determine the reaction’s direction given the equilibrium constant, reactant and product concentrations, and the equilibrium constant.
9.Determine the equilibrium concentrations from the beginning concentrations and the equilibrium constant.
10.Utilize the Le Chatelier’s concept to foresee how altering a system’s concentrations, volume, or temperature will impact the equilibrium position.

Reversible and Irreversible Reactions:

We know that products are formed through chemical reactions between specific raw components, called reactants. An irreversible reaction is one in which all of the reactants are transformed into the products. The direction of movement will be favoured by this reaction to be forward, from the left side of the reactants to the right side (products side). We depict irreversible processes with straight arrows ->.

While reversible means that the results of a reaction can be used to recreate the original reactants through further reactions. indicates the reaction will proceed counterclockwise, from the right (product side) to the left (reactants side). Because of this, it follows that reversible reactions are perpetual and never stop. Both forward and backward directions of the reversible reaction take place simultaneously. Double arrows represent reversible reactions .

Reversible reactions play an important role in establishing dynamic equilibrium.

Dynamic Equilibrium:
When a reaction is taking place in both the forward and backward directions at once, we have reached dynamic equilibrium, according to one definition. Accordingly, we have already stated that reversible processes contribute to the establishment of dynamic equilibrium.


As an example of dynamic equilibrium, consider what happens to a liquid when it is heated in an airtight container and begins to evaporate. Some of the vapours will condense and revert to a liquid form when they rise and collide with liquid surfaces. It follows that the system exhibits both evaporation (ahead reaction) and condensation (following reaction) at the same time (reverse reaction).

Examples of Reversible Reaction:

A reversible reaction is shown by a double-headed arrow connecting the reactants and the products. Sulfur trioxide is produced when sulphur dioxide and oxygen react at 450 degrees Celsius and 200 atmospheres in the presence of vanadium pentoxide as a catalyst. This is a forward reaction because the reactants proceed forward to form the products. At the outset of the forward reactions, the concentration of sulphur trioxide will be 0 because no reaction takes place and no product is formed.

The rate of the forward reaction will increase over time, while the rate of the backward reaction will eventually reach zero. As the product (sulfur-trioxide) is created, the concentration of the reactants (sulphur dioxide and oxygen) will begin to decrease on the left side, and the forward reaction rate will begin to decrease after some time. With the forward reaction slowing, the reverse reaction will speed up. Once again, oxygen and sulphur dioxide will be created from the product, sulphur trioxide. The reactants and the products are said to be in equilibrium if and only if the forward and reverse reaction rates are equal.
Since both forward and reverse reaction rates are equal in this state, we call it chemical equilibrium.
The chemical process is considered to be in equilibrium when the concentrations of the reactant and the product are both equal.

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