Paper 2 - Topic 6, The Rate And Extenet Of Chemical Change Flashcards
What is the activation energy
The minimum amount of energy that particles must collide with to react
What is a catalyst
A catalyst increases the rate of reaction by providing a different pathway for the reaction that has a lower activation energy, they aren’t used up during the reaction
What is the collision theory
According to this theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy
What is the effect of changing concentration on equilibrium
- If the concentration of a reactant is increased, more products will be formed until equilibrium is reached again
- if the concentration of a product is decreased, more reactants will react until equilibrium is reached again
What is the effect of changing pressure on equilibrium
- an increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules
- a decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules
What is the effect of changing temperature on equilibrium
- if the temp of an equilibrium system is increased then the relative amount of products at equilibrium increases for an endothermic reaction and decreases for an exothermic reaction
What is the effect of concentration on reaction rate
Increasing the concentration of reactants in solution means the reacting particles will be closer so they will collide more often so there will be a higher rate of successful collisions and faster rate of reaction
What is the effect of pressure on reaction rate
Increasing the pressure of gaseous reactants means the reacting particles will be closer together, this means they will collide more often so there will be a higher rate of successful collisions and a faster rate of reaction
What is the effect on surface area on reaction rate
Increasing the surface area means there are more exposed reacting particles, this means there are more frequent successful collisions so the rate of reaction increases
What is the effect of temperature on reaction rate
Increasing the temp means particles will have more kinetic energy so will move faster. If the molecules are moving faster they will collide more often and, since they’ve gained KE, a larger proportion of the particles will have at least the activation energy, so the rate of reaction increases
What is the equilibrium
When a reversible reaction occurs in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate
What is Le Chatelier’s Principle
If a reaction is subjected to a change in concentration, temperature or pressure, the position of equilibrium will move to counteract the change
What is the rate of reaction
The measure of the amount of product formed or reactants used over time, units: g/s, cm3 or mol/s
What is a reversible reaction
Reactions in which the products from the reaction can react together to form the original reactants, the direction of reversible reactions can be changed by changing the conditions
How do you find the rate of reactions graphically
- draw tangents to curves and use the slope of the tangent
- calculate the gradient of a tangent to the curve on these graphs as a measure of rate of reaction at a specific time
