In fact, the main reason for using high pressures is to improve the percentage of ammonia in the equilibrium mixture, while it also increases the rate of reaction. Surface area The reaction rate increases with an increase in the surface area of the reactants. The explanation Reactants only react if their particles collide effectively Increasing the surface area of the reactants results in more reaction sites. (Reaction sites - specific sites on molecules at which reactions occur). Increasing the number of reaction sites increases the frequency of total collisions. More effective collisions per unit time will occur which will increase the reaction rate. Example The most effective way of increasing the surface area of a solid is to grind the solid into a powder. Imagine a reaction between magnesium metal and a dilute acid like hydrochloric acid. The reaction involves collision between magnesium atoms and hydrogen ions. Nature of the reacting substances Chemical reactions are usually linked to the breaking of chemical bonds in the reagents and the formation of new bonds to form products. During a chemical reaction the bonds in the reactant molecules have to be broken to form free atoms. These free atoms can then rearrange to form new bonds. The bond energy needed to break the existing bonds in reactant molecules varies according to the nature of the reactants. Different reactants have different energies of activation. Reaction between polar or ionic molecules is very fast. Oxidation-Reduction reactions are slower than ionic reactions because they involve transfer of electrons and bond rearrangement. The physical state of reacting substances is important in determining their reactivity. The reaction in which ionic solutions are involved also take place at high speed (figure below).
In fact, the main reason for using high pressures is to improve the percentage of ammonia in the equilibrium mixture, while it also increases the rate of reaction. Surface area The reaction rate increases with an increase in the surface area of the reactants. The explanation Reactants only react if their particles collide effectively Increasing the surface area of the reactants results in more reaction sites. (Reaction sites - specific sites on molecules at which reactions occur). Increasing the number of reaction sites increases the frequency of total collisions. More effective collisions per unit time will occur which will increase the reaction rate. Example The most effective way of increasing the surface area of a solid is to grind the solid into a powder. Imagine a reaction between magnesium metal and a dilute acid like hydrochloric acid. The reaction involves collision between magnesium atoms and hydrogen ions. Nature of the reacting substances Chemical reactions are usually linked to the breaking of chemical bonds in the reagents and the formation of new bonds to form products. During a chemical reaction the bonds in the reactant molecules have to be broken to form free atoms. These free atoms can then rearrange to form new bonds. The bond energy needed to break the existing bonds in reactant molecules varies according to the nature of the reactants. Different reactants have different energies of activation. Reaction between polar or ionic molecules is very fast. Oxidation-Reduction reactions are slower than ionic reactions because they involve transfer of electrons and bond rearrangement. The physical state of reacting substances is important in determining their reactivity. The reaction in which ionic solutions are involved also take place at high speed (figure below).