the rate and extent of chemical change Flashcards
(24 cards)
what does the rate of chemical reactions mean
the speed at which the reactants get turned into products
what is the equation to work out the average rate of reaction
rate of reaction = quantity of reactants used / time taken (for change to occur)
OR
rate of reaction = rate of products formed / time taken
how do you calculate the rate of reaction at a specific time from a graph
calculate the gradient of the curve at the point asked for (for example 2 minutes) using a tangent remember gradient = change in y / change in x
what happens to the mass of reactants when they are first combined together compared to near the end of the reaction
the mass of the reactant would fall rapidly at first and then slow as the reaction progresses as it gets used up
what are the main factors that effect the rate of reaction
pressure/concentration , temperature, surface area, catalyst
what is the collision theory
in order for particles to react they have to collide with each other with sufficient energy
define activation energy
the minimum energy required for a reaction to take place between reacting particles
what are the two general factors that the rate of reaction depend on if we think about a reaction including tons of particles
- the amount of energy the particles have
- the frequency of collisions
how does temperature effect the rate of reaction
as temp increases the particles gain more energy meaning they move faster therefore they will collide more frequently and with more energy and therefore are more likely to reach their activation energy.
higher rate of successful collisions and higher rate of reaction
how does concentration and pressure effect the rate of reaction
when increased there will be more particles per unit of volume making collisions more frequent increasing the rate of reaction
how does surface area effect the rate of reaction
higher surface area will increase the rate of reaction as there is more space for other reactants to collide, increasing the frequency of collisions leading to a higher rate of reactions
what are catalysts
substances that speed up a reaction without being used up in the reaction itself
how do catalysts effect the rate of reaction
they lower the activation energy by offering an alternate reaction pathway therefore there will be more successful collisions
what do reaction profiles show
the change in the chemicals energy during a reaction
what is meant by a reversible reaction
the products of a reaction can react to reform the reactants
if a reversible reaction is exothermic in one direction what will happen in the other direction
it will be endothermic
what happens if we heat hydrated copper sulphate
it will react to form anhydrous copper sulphate and water. we can then take the products and react them back to form hydrated copper sulphate. this is exothermic and will release heat
define the point of equilibrium
when the forward and reverse reaction take place at the same rate in a closed system
what is meant by the position of equilibrium
if there are more products formed than reactants in a reversible reaction at one point in time the equilibrium will be shifted to the right
how can the position of equilibrium change
dependent on the conditions such as temperature
what is le chateliers principle
if you change the conditions of a reversible reaction, the position of equilibrium will shift to try and counteract that change
what is the effect of changing the temperature on equilibrium if the forward reaction was exothermic
if we decreased the temperature of the system the equilibrium will move in the exothermic direction ( right) in order to release heat energy and counteract the change. equilibrium will then more to right and we would have more products.
increase temp = opposite
what is the effect of changing the pressure on equilibrium
if we increased pressure, equilibrium will more to whichever side that reduces the pressure back down ( the side with the least number of molecules as pressure is how many particles)
decrease = opposite
what is the effect of changing the concentration on equilibrium
if add more reactants it will increase concentration and will shift to the right to form more products
