| What is rate of reaction? | change of concentration of reactants or products per unit time
average rate = change in conc / time
can be measured by the rate at which product is produced
or measuring the rate at which mass decreases
changes in colour |
| What are ways to measure amount of gas produced (inaccurate / more accurate way) | measuring cylinder
gas burette / gas syringe |
| average rate formula | change in volume / time |
| how can the rate at any particular time be seen on a graph? | given by the gradient at that time |
| reasons for inaccuracies in gas experiments? | some gas would escape before the bung is put on the flask (lower co2 gas than expected)
variations in the sizes of the calcium carbonate pieces |
| Average rate formula with mass? | change in mass / time |
| What is collision theory? (2) | for a reaction to happen particles must collide with a certain min amount of energy (Activation energy) and must collide with the correct orientations to create a successful collision |
| what is the min amount of energy needed called? | activation energy is the energy needed to overcome repulsions and start breaking bonds to rearrange atoms
if 2 particles w less than the activation collide, they will just bounce off with no reaction |
| What is the transition state? | as 2 particles get closer the repulsion bw the atoms increases the potential energy and the products bonds start to form which happens during the highest point in the graph = transition state
as the product bonds form = potential energy falls ( bec bond making releases energy) |
| What happens if molecules collide with the wrong orientation? | they wont react |
| What are the factors affecting reaction rate? (5) | concentration of reactants
pressure for gases
surface area of solid reactants
temperature
catalysts |
| What is the effect of concentration on the reaction rate? | with more particles the particles will collide more frequently = greater chance of a successful collisions in a certain TIME |
| What is the effect of pressure on the reaction rate? | increasing pressure increases the collision frequency for gases bec the particles are closer together |
| What is the effect of surface area of solid reactants on reaction rate? | making a solid more finely divided increases the SA as there are more particles exposed at the surface |
| What is the average kinetic energy of particles in gas proportionate to? (5) | its temp in kelvin
so if a sample of O2 is heated from 300K to 600K the average energy of particles is doubled as well
difference in gas types does not affect the average kinetic energy but mass does so
lighter particles will travel faster than heavier ones |
| what effect does temp have on rate of reaction? (4) | as temp increases so does ROR
rise in temp of 10K causes the reaction rate to be doubled
this is bec the molecules have more energy = move faster = collision F increases = collide more often
but the main reason is that they collide harder and with more energy so there is a greater chance that a collision will happen
so increase in the number of particles with energy greater than or equal to activation energy |
| What does the Maxwell Boltzmann distribution show? | only a few particles are at high energy or low energy as most is around average
no molecules has 0 kinetic energy
area under curve represents the total no of particles and wont change as the temp changes |
| how does change in temp look on a graph? | curve is flatter
and max has moved to the right = fewer particles w lower energy and more w higher energy
greater proportion of successful collisions = ROR increases
area under curve is the same bec the no of particles does not change |
| What is a catalyst? | a substance that increases the rate of a chemical reaction without being used up
important in many industrial processes
acts by allowing the reaction to happen in an alt pathway of lower activation energy
lower activation energy means it moves to the left = more particles at the right energy to react |
