reaction rates and equilibrium- 10.1- reaction rates Flashcards
(12 cards)
what is the rate of chemical reaction?
The change in concentration of a reactant or product
what is the formula for rate of reaction?
rate= change in concentration/ time (mol dm-3 s-2)
describe how rate changes overtime
-fastest at the start of the reaction, as each reactant is at its highest concentration
-the rate slows down as the reaction proceeds, because the reactants are being used up and their concentrations decrease.
-once one of the reactants has been completely used up, the concentration stops changing and the rate is zero
What factors can change the rate of reaction?
-concentration (pressure for gases)
-temperature
-use of a catalyst
-SA of solid reactants
what is collision theory?
2 reacting particles must collide for a reaction to occur.
What 2 things are required for a successful collision?
-correct orientation
-sufficient energy to overcome the Ea.
How does increasing concentration affect rate of reaction?
-increasing concentration, increases rate of reaction.
-It increases the number of particles in the same volume, particles are more close together and collide more frequently, in a given period of time there will therefore be more effective collisions.
How does increasing the pressure of a gas affect the rate of reaction?
When a gas is compressed into a smaller volume, the pressure is increased and rate of reaction increases.
The concentration of the gas molecules increases as the same number of gas molecules occupy a smaller volume. The gas molecules are closer together and collide more frequently, leading to more effective collisions.
How can the progress of a chemical reaction be followed?
-monitoring the removal of a reactant (decrease conc)
-monitoring the formation of a product (increase in conc)
e.g. gas volume, mass, colour
What 2 methods can be used to determine rate of reaction if it produces a gas.
-monitoring the volume of gas produced at regular time intervals using gas collection
-monitoring the loss of mass of reactants using a balance
How to monitor the production of a gas using gas collection for the decomposition of hydrogen peroxide.
- Hydrogen peroxide is added to a conical flask and the bung is replaced.
- The initial volume of gas in the measuring cylinder is recorded.
- Manganese dioxide (catalyst) is then quickly added to the conical flask and the bung is replaced. A stop clock is started.
- The volume of gas produced in the measuring cylinder is recorded at regular intervals until the reaction is complete.
- The reaction is complete when no more gas is produced.
How to calculate the initial rate of reaction on a graph?
draw a tangent at t=0 and calculate the gradient
