C8 Flashcards
How can you work out the rate of reaction?
By finding how quickly the reactants are used up as they make products or by the products being made.
How can you measure the decreasing mass of a reaction mixture?
You can measure the rate at which the mass of a reaction changes if the reaction gives a gas. You put a conical flask on a scale and add hydrochloric acid and marble chips, adding a cotton bung to the top to let out gas but not let vapour escape. You measure the change in results.
How can you measure increasing volume of gas given off?
If the reaction produces a gas you can use a gas syringe added to a reaction mixture in a conical flask or you can get a measuring cylinder filled with water and watch as the gas displaces the water.
How to calculate mean rate of reaction?
mean rate of reaction=quantity of reactant used/time
or quantity of product formed/time
What is collision theory?
When reactions only take place when the particles of reactants come together. They need to bump into each other with enough energy to cause a reaction to take place.
What is activation energy?
It is the minimum amount of energy that particles must have before they can react.
What are the 5 factors affecting rate of reaction?
Surface area, concentration, temperature, pressure and catalysts
How does surface area impact rate of reaction?
If there is a large lump of reactant, then the reactant will react slowly as less is in contact with the other reactant and if it is in small lumps then more area will be in contact with the other reactant.
How does temperature impact rate of reaction?
Particles collide more often and with more energy. An increased proportion of particles exceeding the activation energy has a greater effect than the increased frequency of collisions.
How does pressure and concentration impact the rate of reaction?
Pressure and concentration, if high, will result in more collisions.
What are catalysts and how do they work?
They are things that speed up reactions by lowering the activation energy. They make a higher proportion of the reactant particles have sufficient energy to react which means the frequency of effective collisions increases and the rate of reaction speeds up.
What is a reversible reaction?
A reaction where the products of the reaction can react to make the original reactants. It can be shown with the arrows going both ways
Where does the energy go in a reversible reaction?
One reaction in a reversible reaction is endothermic and one is exothermic. In any reversible reaction the amount of energy transferred to the surroundings when the reaction goes one direction is exactly equal to the energy transferred back when the reaction goes the other way.
What is a closed system?
It is where no reactants can get in or out.
What is equilibrium in a reaction?
Where there is no change in the amount of products and reactants, where the rate of the forward reaction equals the rate of the reverse reaction.
What is Le Chatelier’s principle?
He noticed whenever a change in conditions were introduced to a system in equilibrium, the position of equilibrium shifts as to cancel out the change. The change in conditions can be changes in concentration, pressure or temperature.
How can changing pressure change the amount of products made?
If the forward reaction produces more molecules of gas then an increase in pressure decreases the amount of products formed and vice versa. However, if the forward reaction produces fewer molecules of gas, an increase in pressure increases the amount of products formed and vice versa.
How can changing temperature change the amount of products made?
If the forward reaction is exothermic, an increase in temperature decreases the amounts of products formed and vice versa. However, if the forward reaction is endothermic, an increase in temperature increases the amount of products formed and vice versa.
