Question

Which of the following statements is not correct? (a) Catalyst action is specific. (b) A catalyst does not alter the equilibrium. (c) A small amount of catalyst is sufficient to catalyse a reaction. (d) The catalyst initiates the reaction

Short answer

The incorrect statement is (d) The catalyst initiates the reaction. The catalyst does not initiate the reaction, it only lowers the activation energy, making the reaction faster

Step-by-step solution

Catalyst Action Is Specific

Catalysts are indeed often specific to certain reactions. They provide a different path of minimum energy for the reaction to occur and this path is typically specific to each reaction. So, statement (a) is correct.

A Catalyst Does Not Alter The Equilibrium

Catalysts do not change the equilibrium of a reaction, they only speed up the rate at which the equilibrium is reached. Hence, statement (b) is also correct.

A Small Amount Of Catalyst Is Sufficient

A small amount of catalyst is usually enough to catalyze a reaction. This is because the catalyst is not consumed in the reaction, allowing it to continue to catalyze the reaction as long as it is present. Therefore, statement (c) is also correct.

The Catalyst Initiates The Reaction

The catalyst itself does not initiate the reaction. It only provides a new pathway with lower activation energy for the reaction to occur. The reaction would still take place without the catalyst, just at a slower rate. So, statement (d) is incorrect as the catalyst does not initiate the reaction.

Key concepts

Chemical Equilibrium

Chemical equilibrium is a state in a chemical reaction where the concentrations of reactants and products remain constant over time. This happens because the forward and reverse reactions occur at the same rate. It is important to note that equilibrium is dynamic, meaning that reactions are still happening, but there is no net change in the concentration of substances.

When a catalyst is introduced to a reaction at equilibrium, it speeds up both the forward and reverse reactions equally. This means that the position of equilibrium does not change. Instead, the rate at which equilibrium is reached increases. Here are at some critical points about chemical equilibrium:

• Catalysts do not shift the equilibrium position.
• The amounts of reactants and products stay constant.
• Equilibrium can be reached from either direction of reaction.

Understanding chemical equilibrium is vital because it helps predict how a system will respond to changes such as temperature or pressure.

Activation Energy

Activation energy is the minimum amount of energy required for a chemical reaction to take place. It's like the "cost" that molecules need to "pay" to react. When molecules collide, they need to have enough energy to break and form new bonds to turn into products. This required energy is the activation energy ( E_a ).

Catalysts play a vital role by lowering the activation energy, which makes it easier for reactions to occur. They provide an alternative reaction pathway with a lower energy barrier. Because of this, reactions happen faster with a catalyst. Here are some features of activation energy and catalysts:

• A lower activation energy increases the reaction rate.
• Catalysts do not alter the energy of reactants or products.
• They only affect the speed of the reaction.

While removing the "hurdle" of high activation energy, catalysts allow more molecules to participate in the reaction at a given temperature, leading to a faster reaction rate.

Reaction Rate

The reaction rate is the speed at which a chemical reaction takes place. It tells us how fast the reactants convert into products. Several factors can influence the rate of a reaction, including temperature, concentration of reactants, surface area, and the presence of catalysts.

Catalysts are particularly important because they increase the reaction rate without being consumed in the process. They work by lowering the activation energy, allowing more molecules to reach the energy needed for the reaction more quickly. Some important points regarding reaction rates include:

• Catalysts make reactions happen faster but do not change the amount of product formed.
• Increased reactant concentration generally raises the reaction rate.
• Higher temperatures provide more energy to molecules, increasing the rate.

By understanding and controlling reaction rates, chemists can optimize industrial processes and develop effective strategies for new reactions.