c8 Flashcards
equation for mean rate of reaction
quantity of reactant used or product formed / time taken
what is the unit for the rate of reaction?
g/s or cm^3/s
how can the quantity of reactant or product be measured?
mass in grams or volume in cm^3
what are the factors which affect the rate of reaction?
the concentration of reactants in solution
the pressure of the reacting gases
the surface area of solid reactants
the temperature
the presence of catalysts
how does increasing pressure affect rate of reaction?
increasing pressure would mean there are more particles in a given volume, therefore there would be more collisions so the rate of reaction will increase
how does increasing concentration affect the rate of reaction?
increasing concentration would mean there are more reactant particles moving together so there would be more collisions per unit time and so the reaction rate is increased
how does increasing temperature affect the rate of reaction?
it increases the frequency of collisions and makes the collisions more energetic and so increases the rate of reaction.
how does increased surface area affect rate of reaction?
the particles around it will have more area to work on at increased surface area, so there will be collisions more frequently
what are catalysts?
a catalyst is a substance that speeds up a reaction without being used up in the reaction itself.
how do catalysts affect the rate of reaction?
they reduce the activation energy needed for the reaction to occur by providing an alternative reaction pathway with a lower activation energy.
this would mean that the rate of reaction increases because less energy is required.
what is collision theory?
it states that chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.
what is activation energy?
the minimum amount of energy that particles must have to react
what are enzymes?
they act as catalysts in biological systems
what are reversible reactions?
when the products of the reaction can react to produce the original reactant.
if a reaction is exothermic one way, then it is endothermic the other way.
what is equilibrium?
in a closed system when the rate of forward reaction = rate of reverse reaction
what happens when a change is made to the conditions of a system at equilibrium?
the system responds to counteract the change - le chatelier’s principle
effect of changing concentration in an equilibium
if the concentration of the reactants increase, more products will be formed until equilibrium is reached
if the concentration of the products decrease, more reactants react until equilibrium is reached again.
effect of when temperature increases of a system at equilibrium
equilibrium moves in the endothermic direction to reverse the change
effect of when temperature decreases of a system at equilibrium
equilibrium moves to the exothermic direction to reverse the change
effect of when pressure increases of a system at eqilibrium
equilibrium position shifts to side with smaller number of molecules to decrease the pressure again
effect of when pressure decreases of a system at eqilibrium
equilibrium position shifts to side with larger number of molecules to increase the pressure again
how can u measure the rate of reaction by measuring the change in mass - practical
set up a conical flask with the solution and cover it will cotton wool at the top of the flask - this is so that the gas can escape but the acid cannot. put this on a weighing scale and start the timer.
as the gas is released, the mass disappearing is measured on the balance. th quicker the reading drops, the faster the reaction.
it is accurate because the balance is quite accurate, however, it releases the gas straight into the room
measuring rate of reaction by observing the colour change
add your solution into a conical flask uing a measuring cylinder and place over a black cross. add your acid and swirl. start a stopwatch. the solution should turn cloudy. stop the stopwatch when you can no longer see the black cross. repeat using different concentrations of the solution. repeat whole experiment to calculate a mean and draw a graph.
what is reproducibility?
if a measurment can be repeated by someone else or using a different technique and you can get the same results
measuring volume of gas to see the rate of reaction
use measuring cylinder and place a certain volume of the acid into a conical flask. attach it to a bung and delivery tube. place the delivery tube into a container filled with water. then place an upturned measuring cylinder also filled with water over the delivery tube. add the metal strip into the conical flask and start the stopwatch. the reaction will prouce a gas which will be trapped in the measuring cylinder and the volume can be measured.
repeat experiment with different concentrations.
