Rate of ReactionCambridge IGCSE Chemistry: Flashcards

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Define 'rate of reaction'.

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Define 'rate of reaction'.: The rate of reaction is the speed at which reactants are converted into products, measured as the change in concentration of a substance per unit time, or the change in mass or volume of a substance per unit time.
How does increasing the concentration of a solution affect the rate of reaction?: Increasing concentration increases the rate of reaction because there are more particles per unit volume, leading to more frequent collisions between reactant particles.
How does increasing the pressure of gases affect the rate of reaction?: Increasing pressure increases the rate of reaction because the gas particles are forced closer together, increasing the number of particles per unit volume and the frequency of collisions.
How does increasing the surface area of a solid affect the rate of reaction?: Increasing the surface area of a solid increases the rate of reaction because more of the solid is exposed to reactants, allowing more particles to collide per unit time.
How does increasing temperature affect the rate of reaction?: Increasing temperature increases the rate of reaction because particles gain more kinetic energy, move faster, collide more frequently, and a greater proportion of collisions have sufficient energy to exceed the activation energy.
What is a catalyst?: A catalyst is a substance that increases the rate of a chemical reaction without being chemically changed or used up at the end of the reaction.
How does a catalyst increase the rate of reaction according to collision theory?: A catalyst decreases the activation energy (Ea) required for a reaction to occur, meaning more particles have sufficient kinetic energy to react when they collide, increasing the reaction rate.
What is an enzyme?: An enzyme is a biological catalyst, usually a protein, that speeds up specific chemical reactions in living organisms without being permanently changed.
Describe the method for investigating rate of reaction using change in mass.: Place reactants in a container on a balance, record the mass at regular time intervals as gas is released, and plot a graph of mass loss against time. The gradient indicates the reaction rate.
Describe the method for investigating rate of reaction using formation of a gas.: Collect gas produced in a measuring cylinder or gas syringe at regular time intervals, or use an inverted burette over water. Plot volume of gas against time; the gradient shows the reaction rate.
What does collision theory state about the kinetic energy of particles?: Collision theory states that particles must collide with sufficient kinetic energy (equal to or greater than the activation energy) for a reaction to occur when they collide.
Define 'activation energy' (Ea).: Activation energy is the minimum amount of kinetic energy that particles must have when they collide for a reaction to occur.
Explain how concentration affects rate of reaction using collision theory.: Increasing concentration increases the number of particles per unit volume, so the frequency of collisions increases, leading to more collisions per unit time and a faster reaction rate.
Explain how temperature affects rate of reaction using collision theory.: Increasing temperature increases the kinetic energy of particles, causing them to move faster and collide more frequently. Additionally, a larger proportion of collisions exceed the activation energy, so more collisions are successful.
Name two advantages and one disadvantage of the gas collection method for measuring rate of reaction.: Advantages: results are easy to record and plot, and the method works well for fast reactions. Disadvantage: gas may dissolve in water or be difficult to collect completely, leading to inaccurate measurements.