Topic 6 - The Rate And Extent Of Chemical Change Flashcards
What is the rate of a chemical reaction
The rate of a chemical reaction is how fast the reactants are changed into products
What is one of the slowest rates of reaction
The rusting of iron
What is an example of a moderate speed reaction and a fast reaction
A moderate speed reaction would be magnesium reacting with an acid to produce a gentle stream of bubbles
Burning is a fast reaction but explosions are even faster and release a lot of gas..
What must happen in order for reaction to occur
Particles must collide with enough energy in order to react. Reaction rates are explain personally by collision theory
What does the rate of a chemical reaction depends on
The collision frequency of reacting particles. The more collisions there are the faster the reaction is
The energy transfer gional condition. Particles have to collide of enough energy for the collection to be successful.
What is the activation energy
The activation energy is the minimum amount of energy that particles need to react. Particles need this much energy to break the bonds in the reactants to start reaction
What are the four things that the rate of reaction depends upon
Temperature
Surface area
The presence of a catalyst
The concentration of a solution or the pressure of gas
How does increasing the temperature increases the rate of reaction
When the temperature is increased, the particles all move faster
If they’re moving faster they going to collide more frequently
Also the faster they move the more energy they have some more of the collisions will have enough energy to make the reaction happen
How does increasing the concentration or pressure increase the rate of reaction
If a solution is made more concentrated, it means there are more particles knocking about in the same volume of water
Similarly when the pressure of the gas is increased, it means that the same number of particles occupies a smaller space which means collisions between the reactant particles are more frequent
How does increasing the surface area increase the rate of reaction
If one of the reactants is a solid, then breaking it up into smaller pieces would increase the surface area to volume ratio which means that for the same volume of the solid, the particles around it will have more area to work on so there will be more frequent collisions
How does using a catalyst increases the rate of reaction
Different catalysts are needed for different reactions but they will work by decreasing the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy
What are enzymes
Enzymes are biological catalysts. They catalyse reactions in living things
What is a catalyst
A catalyst is a substance that speeds up a reaction without being used up in the reaction itself
How do you work out the rate of reaction when given the amount of reactant used or amount of products formed and time
Rate of reaction = amount of reactant used or amount of product formed/time
What are three different ways of measuring the rate of reaction
Precipitation and colour change
Change in mass (usually gas given off)
The volume of gas given off
How do you measure the rate of reaction through the change in mass
Measuring the speed of reaction that produces a gas can be carried out using a mass balance
As the gases released the mass disappearing is measured on the mass balance
The quicker the reading on the mass balance drops the faster the reaction is
This is the most accurate of the three methods because the mass balance is very accurate however has the disadvantage of releasing the gas straight into the room
How do you measure the rate of reaction through the volume of gas given off
Involves the use of a gas syringe to measure the volume of gas given off
The more gas given off during a given time interval the faster the reaction
How do you find the mean rate for a whole reaction on a graph
You just work out the overall change in the Y value and then divide this by the total time taken for the whole reaction
What is a dynamic equilibrium
A dynamic equilibrium means the concentrations of reactants and products have reached a balance and won’t change
When is equilibrium only reached
Equilibrium is only reached if the reversible reaction takes place in a closed system so that none of the reactants or products can escape and nothing else can get in
What is an exothermic reaction
And exothermic reaction is where energy leaves the reaction
Exit
What is le chatliers principal
Le chatliers principle is the idea that if you change the conditions of a reversiblereversible reaction at equilibrium, the system will try to counteract the change
It can be used to predict the effects of any changes you make to reaction system
