4.3 - Applications of the Concept of Rate of Reaction

Application in Daily Life

• Factors affecting the rate of reaction can be adjusted to increase or decrease the rate of a reaction.
• A refrigerator lowers the temperature of food and drinks.
• The lower temperature slows down the rate of food spoilage.

Haber Process

The Haber Process produces ammonia, $\mathrm{N}{\mathrm{H}}_3$.

Conditions

• Reactants: nitrogen gas, ${\mathrm{N}}_2$, and hydrogen gas, ${\mathrm{H}}_2$.
• Ratio of nitrogen to hydrogen: 1 : 3.
• Temperature: $450^{\circ }\text{C}$–$550^{\circ }\text{C}$.
• Pressure: $200\text{atm}$.
• Catalyst: iron filings, $\mathrm{Fe}$.

Reaction

Process flow

1. Nitrogen gas and hydrogen gas are mixed in a 1 : 3 ratio.
2. The gas mixture is compressed to $200\text{atm}$.
3. The compressed gases pass through a reactor containing iron filings at $450^{\circ }\text{C}$–$550^{\circ }\text{C}$.
4. Ammonia gas produced is cooled to form liquid ammonia.
5. Unreacted nitrogen and hydrogen gases are channelled back into the process.

Contact Process

The Contact Process produces sulphuric acid, ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$.

Stage 1: production of sulphur dioxide

• Sulphur is burnt in excess air.

Stage 2: production of sulphur trioxide

• Sulphur dioxide is mixed with excess air.
• The gas mixture passes over vanadium(V) oxide catalyst at $450^{\circ }\text{C}$ and $1\text{atm}$.

Stage 3: production of oleum

• Sulphur trioxide is dissolved in concentrated sulphuric acid to produce oleum, ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_7$.

Stage 4: production of concentrated sulphuric acid

• Oleum is diluted with water.

Industrial Conditions at a Glance

Haber Process	Contact Process
Product: ammonia	Product: sulphuric acid
Temperature: $450^{\circ }\text{C}$–$550^{\circ }\text{C}$	Temperature: $450^{\circ }\text{C}$
Pressure: $200\text{atm}$	Pressure: $1\text{atm}$
Catalyst: iron filings	Catalyst: vanadium(V) oxide

The controlled factors that increase the rate of reaction in these industrial processes are temperature, pressure and presence of catalyst.