Question

Hydrogen cyanide is produced industrially by the following exothermic reaction:

$\mathbf{2}\mathit{N}{\mathit{H}}_{\mathbf{3}}\left(\mathit{g}\right)\mathbf{+}\mathbf{3}{\mathit{O}}_{\mathbf{2}}\left(\mathit{g}\right)\mathbf{+}\mathbf{2}\mathit{C}{\mathit{H}}_{\mathbf{4}}\left(\mathit{g}\right)\underset{\mathbf{P}\mathbf{t}\mathbf{-}\mathbf{R}\mathbf{h}}{\overset{{\mathbf{1000}}^{\mathbf{o}}\mathbf{C}}{\mathbf{\to }}}\mathbf{2}\mathit{H}\mathit{C}\mathit{N}\left(\mathit{g}\right)\mathbf{+}\mathbf{6}{\mathit{H}}_{\mathbf{2}}\mathit{O}\left(\mathit{g}\right)$

Is the high temperature needed for thermodynamic orfor kinetic reasons?

Short answer

The high temperature is needed for kinetic reasons but not for thermodynamic reasons

Step-by-step solution

Step 1: Introduction to the Concept

The ratio of thermal energy to the temperature at which work cannot be done is known as entropy. It's also known as the measure of a system's molecular disarray. It has a lot of properties and state functions.

Chemical reactions can be used to demonstrate how kinetic and thermodynamics are related to one another.

Thermodynamics is tied to stability, whereaskinetics is linked to reactivity.

The most stable states in a kinetic reaction are those of reactants, where energy is required to advance the reaction from a state of stability to one of reacting and subsequently transforming into products.No energy is required to move the reaction in a thermodynamic reaction because it occurs spontaneously, and the most stable states are the reaction's products.

Step 2:Explanation

From the given reaction:

$2N{H}_3\left(g\right)+3O_2\left(g\right)+2C{H}_4\left(g\right)\underset{Pt-Rh}{\overset{{1000}^{o}C}{\to }}2HCN\left(g\right)+6H_{2}O\left(g\right)$

Thesign of entropy is positive in this situation because the number of moles of products in the gaseous state is greater than the number of moles of reactants.

The enthalpy is negative because the reaction is exothermic; therefore, any reaction at a temperature above OK has anegative Gibbs free energy.

As a result, the reaction is both spontaneous and thermodynamically advantageous.

Now, in kinetics, energy is necessary to move the reaction, necessitating a high temperature for reaction feasibility.

As a result,high temperatures are needed for kinetic rather than thermodynamic reasons.