4.6 The rate and extent of chemical change Flashcards
(17 cards)
What is the rate of a chemical reaction?
The speed at which reactants are converted into products, measured by the change in concentration of reactants or products over time.
How is the rate of reaction calculated from a graph?
It is the gradient of the line on a concentration vs time graph, steeper means faster reaction.
What are the four main factors that affect the rate of reaction?
Temperature, concentration (or pressure for gases), surface area of reactants, and the presence of a catalyst.
How does increasing temperature affect the rate of reaction?
It increases the kinetic energy of particles, leading to more frequent and energetic collisions, resulting in a higher reaction rate.
How does concentration affect the rate of reaction?
Higher concentration means more particles are present in a given volume, leading to more collisions and a faster reaction rate.
How does pressure affect the rate of reaction in gases?
Higher pressure compresses the gas molecules, increasing their concentration and thus the frequency of collisions, speeding up the reaction.
How does surface area affect the rate of reaction?
Smaller particles (e.g., powdered solid) have a larger surface area for collisions to occur, thus increasing the rate of reaction.
What is a catalyst?
A substance that increases the rate of a reaction by providing an alternative reaction pathway with lower activation energy, without being used up in the process.
What is the collision theory?
A theory stating that for a reaction to occur, particles must collide with sufficient energy (activation energy) and in the correct orientation.
What is activation energy?
The minimum amount of energy required for particles to collide and react, breaking bonds and forming new ones.
What is a reversible reaction?
A reaction where the products can react to form the original reactants, and the reaction can go in both directions.
What is dynamic equilibrium?
When the rate of the forward reaction equals the rate of the backward reaction in a closed system, leading to constant concentrations of reactants and products.
What is Le Chatelier’s Principle?
When a system at equilibrium is disturbed, it shifts in the direction that opposes the change, to restore equilibrium.
How does increasing temperature affect equilibrium?
It favours the endothermic reaction (which absorbs heat) to counteract the temperature rise.
How does increasing pressure affect equilibrium?
It favours the side of the reaction with fewer gas molecules, to reduce pressure.
How does changing concentration affect equilibrium?
The system will shift to use up the added substance or produce more of the removed substance to counteract the change.
What is the Haber Process?
The industrial process used to make ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂), using iron as a catalyst and high pressure and temperature.
