7.3.1 Applications of Factors that Affect the Rate of Reaction

Applications of Rate of Reaction

Keeping food in a refrigerator

If food is kept in the fridge, the food will keep longer because the low temperature will slow down the rate of the chemical reaction which destroys food.

Cooking food in a pressure cooker

  1. In a pressure cooker, the high pressure causes the water in the cooker to boil at a temperature of more than 100°C.
  2. At a higher temperature, the time for the food to get cooked is decreased.

Cooking Food in Small Pieces

Food in the shape of big pieces has a surface area per volume which is small, so the heat takes a longer time to reach the inside of the food. So, to cook faster, the food needs to be cut into smaller pieces.

Making Margarine
  1. Vegetable oil is an organic compound that is not saturated and exists in the liquid state at room temperature. 
  2. Through investigation and continuous development, vegetable oil can be changed to margarine through the process of hydrogenation using nickel as a catalyst at a temperature of 180°C.

Breakdown of Petroleum

  1. Big molecules of hydrocarbon obtained during fractional distillation of petroleum have been found to be less useful than small molecules of hydrocarbon. 
  2. The breakdown process with the use of the catalyst alumina produces smaller hydrocarbons.

Burning of Coal

  1. Coal contains the element carbon. Burning of coal in the air that is in excess will produce carbon dioxide, water, and heat energy.
  2. A big piece of coal takes a long time to burn because the total surface area that is touched by the fire is small.
  3. The rate of burning pieces of coal which are small is higher because the total surface area is bigger. With this, it provides a lot of heat energy in a short period of time.

Haber Process (Produces Ammonia)

  1. In the Haber process, a mixture of nitrogen and hydrogen in the ratio 1:3 is conducted through the powdered iron as a catalyst at a temperature of 450°C to 550°C and a pressure of 200 to 300 atmospheres with molybdenum as a promoter.
  2. Powdered iron is used as the catalyst to raise the rate of reaction.
  3. Also, the reaction is conducted at a high temperature to increase the rate of reaction.
    N₂ + 3H₂ ⟶2NH₃
    (450- 550oC, Iron, 200-300atm)

Contact Process (Produces Sulphuric Acid)

Stage 1
Sulphur is burnt in air to produce sulphur dioxide.
S(s) +  O₂ → SO₂

Stage 2,
Sulphur dioxide that is formed is mixed with excess oxygen and is conducted through the catalyst vanadium (V) oxide to raise the rate of reaction. A temperature of 500°C and a pressure of l to 2 atmospheres is used.
2SO₂(g) +  O₂(g)  → 2SO₃(g)

Stage 3
Sulphur trioxide that is formed is dissolved in concentrated sulphuric acid to form oleum at stage two.
SO₃ +  H₂SO₄ → H₂S₂0₇

Stage 4
Sulphur trioxide does not dissolve directly in the water because this reaction releases too much heat and could even produce an explosion. Then,,, water is mixed with the oleum to produce concentrated sulphuric acid.
H₂S₂O₇ +  H₂O (1) → 2 H₂SO₄( aq )

Ostwald Process (Produces Nitric Acid)

  1. At the first stage, ammonia is oxidized in excess in the presence of platinum as catalyst to produce nitrogen monoxide. The high temperature of 850°C and pressure of 5 atmospheres is used
    4NH₃ ( g )  +  5O₂(g) → 4NO (g) +  6H₂O (1)
  2. Nitrogen monoxide that is formed reacts with oxygen to produce nitrogen dioxide at stage two.
    2NO(g) +  O₂ → 2NO₂
  3. At the final stage, nitrogen dioxide together with excess air is dissolved in hot water at a temperature of 80°C to produce concentrated nitric acid.
    4NO₂(g) +  O₂(g) +  2H₂O (1) → 4HNO₃(g)