Choosing reaction conditions - Higher
Raw materials and energy
The reaction conditions used in an industrial process are related to the availability and cost of:
- raw materialBasic material that goods are made from such as crops, metals, wood and animal products such as wool and leather.
- energyThe capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. supplies
For example, hydrogen can be manufactured by reacting natural gas with steam, or by the electrolysisThe decomposition (breakdown) of a compound using an electric current. of water. The table shows some of the factors involved in choosing between these two methods.
| Natural gas and steam | Electrolysis of water | |
| Raw materials | Natural gas is a non-renewable resource | Water is readily available from rivers, lakes and oceans |
| Energy supplies | Strong heating using natural gas, coal or fuels from crude oil | Electricity can be generated using renewable resources |
| Raw materials | |
|---|---|
| Natural gas and steam | Natural gas is a non-renewable resource |
| Electrolysis of water | Water is readily available from rivers, lakes and oceans |
| Energy supplies | |
|---|---|
| Natural gas and steam | Strong heating using natural gas, coal or fuels from crude oil |
| Electrolysis of water | Electricity can be generated using renewable resources |
Question
A chemical company is planning to open a new factory to manufacture hydrogen. It has found a suitable site for the factory on the coast with nearby off-shore wind turbineRevolving machine with blades that are turned by wind, water or steam. Turbines in a power station turn the generators..
State which method, reacting natural gas with steam or electrolysis of water, is likely to be most suitable. Explain your answer.
Electrolysis of water is likely to be the most suitable. Water is readily available from the sea, and the electricity needed can be generated by the wind turbines.
Reversible reactions
When a reversible reactionA chemical reaction which can go both ways. happens in a closed container, it reaches a dynamic equilibriumIn chemical reactions, a situation where the forward and backward reactions happen at the same rate, and the concentrations of the substances stay the same.. The equilibrium position of a reversible reaction is a measure of the concentrationThe concentration of a solution tells us how much of a substance is dissolved in water. The higher the concentration, the more particles of the substance are present. of the reacting substances at equilibrium.
The table summarises the effects of these factors on the equilibrium position and the time taken to reach equilibrium.
| Change in conditions | Equilibrium position moves | Time taken to reach equilibrium |
| Pressure increased | Towards the fewest molecules of gas | Decreased |
| Concentration increased | Away from that reactant | Decreased |
| Temperature increased | In the direction of the endothermic reaction | Decreased |
| Catalyst added | There is no change | Decreased |
| Change in conditions | Pressure increased |
|---|---|
| Equilibrium position moves | Towards the fewest molecules of gas |
| Time taken to reach equilibrium | Decreased |
| Change in conditions | Concentration increased |
|---|---|
| Equilibrium position moves | Away from that reactant |
| Time taken to reach equilibrium | Decreased |
| Change in conditions | Temperature increased |
|---|---|
| Equilibrium position moves | In the direction of the endothermic reaction |
| Time taken to reach equilibrium | Decreased |
| Change in conditions | Catalyst added |
|---|---|
| Equilibrium position moves | There is no change |
| Time taken to reach equilibrium | Decreased |
Question
Describe the change in reaction conditions which increases the rate of reaching equilibrium, but does not change the position of equilibrium position.
Adding a suitable catalyst.