AQA GCSE Chemistry Topic 6: The Rate and Extent of Chemical Change Quiz

Calculating Rates of Reactions

• Rates of reactions can be measured using the amount of reactant used or product formed over time
• Formula for rate of reaction: Rate of reaction = amount of reactant used ÷ time or Rate of reaction = amount of product formed ÷ time
• Quantity of reactant or product can be measured by mass in grams or by volume in cm³
• Units of rate of reaction may be given as g/s or cm³/s
• Quantity of reactants can also be measured in terms of moles, with units of rate of reaction as mol/s
• To find the rate of reaction graphically, draw tangents to curves and use the slope of the tangent

Factors Affecting Rates of Chemical Reactions

• Concentration of reactants
• Pressure of reacting gases
• Surface area of solid reactants
• Temperature
• Catalysts

Collision Theory and Activation Energy

• Collision theory: chemical reactions can occur only when reacting particles collide with each other and with sufficient energy
• Activation energy: the minimum amount of energy that particles must have to react
• Increasing concentration, pressure, and surface area increases the frequency of collisions and thus the rate of reaction
• Increasing temperature increases the frequency of collisions and makes them more energetic, thus increasing the rate of reaction

Catalysts

• Substances that speed up chemical reactions without being changed or used up during the reaction
• Enzymes act as catalysts in biological systems
• Catalysts decrease the activation energy, increasing the proportion of particles with energy to react
• Catalysts provide a different pathway for a chemical reaction with a lower activation energy

Test your knowledge on calculating rates of reactions, measuring rates of reactions, and understanding the factors affecting the rate of reaction. This quiz covers concepts related to the rate and extent of chemical change in the context of AQA GCSE Chemistry Topic 6.