Chemical Reactions

You will be able to

• Describe the effect of concentration, temperature, surface area and a catalyst on the rate of a reaction.
• Explain each effect using collision theory: collision frequency and the proportion of collisions with energy at least equal to the activation energy.
• Determine the initial rate from the gradient of a volume–time graph and compare runs in a fair test.

You will be able to

• Determine the rate at a given time from the gradient of a tangent to a volume–time or mass-loss–time graph.
• Deduce the limiting reactant from the amounts used and calculate the final volume or mass of gas.
• Explain why the rate decreases during a reaction and how concentration and the limiting reactant change the shape of the curve.

You will be able to

• Describe dynamic equilibrium: forward and backward rates equal and concentrations constant, in a closed system.
• Predict the effect of changing temperature, pressure and a catalyst on the position of equilibrium and on the rate.
• Explain why 450 °C, 200 atm and an iron catalyst are compromise conditions for the Haber process, and state the Contact process conditions.

You will be able to

• Identify oxidation and reduction in terms of oxygen, electrons and changes in oxidation number.
• Identify the oxidising agent and the reducing agent in a redox reaction.
• Describe the colour changes when acidified potassium manganate(VII) and aqueous potassium iodide are used to test for reducing and oxidising agents.