topic six: rate and extent of chemical change Flashcards
give the equations regarding mean rate of reaction
mean rate of reaction = quantity of reactant used / time
mean rate of reaction = quantity of product formed / time
what can the quantity of a chemical be measured in?
mass in grams / volume of gas in cm3 / amount in moles
why do we draw reaction rate graphs?
they can be drawn to show how the quantity of reactant used or product formed changes with time
what does the slope represent in a reaction rate graph?
the rate of reaction thus the steeper the slope, the faster the reaction
how would we find the rate of reaction at a single point?
by drawing a tangent to the curve and calculating the slope
what is the formula for calculating the slope?
change in y / change in x
define activation energy
the minimum amount of energy particles need to react
when do successful collision occur?
when reactant particles collide with enough energy to react
what does the rate of a reaction depend on? (regarding collision theory)
the frequency of successful collisions
how does temperature influence the rate of a reaction?
the higher the temperature, the faster the reaction. this is because the particles have more energy so they have enough energy to react when the collide
how does concentration influence the rate of a reaction?
the higher the concentration, the more particles of a solute that are dissolved. the higher the concentration of reactant in solution, the greater the rate of reaction. this is because there are more reactant particles in the solution meaning a successful collision is more likely to occur.
how does the pressure of reacting gases influence the rate of a reaction?
the greater the pressure of a gas, the closer the reactant particles are together so the higher the pressure the faster the reaction. this is because the reactant particles are closer together so there are more frequent successful collisions.
how does surface area of solid reactant influence the rate of a reaction?
when a solid is in powder form, it has a greater surface area. the greater the surface area, the faster the rate of reaction. this is because there are more particles on the surface that can react so there are more frequent successful collisions.
how does the presence of a catalyst influence the rate of a reaction?
when a catalyst is present, the activation energy is lowered meaning the particles require less energy to react and thus do so more frequently.
define a catalyst
a substance that speeds up a chemical reaction without getting used up in the process
give an example of a biological catalyst
an enzyme e.g. amylase or protease
draw the graph showing the effect of temperature on the rate of a reaction
rate of reaction on the y-axis
temperature on the x-axis
a curved slope meaning it is NOT proportional
draw the graph showing the effect of the concentration of a solution on the rate of a reaction
rate of reaction on the y-axis
concentration of a solution on the x-axis
a straight line from the origin indicating that they are directly proportional (as one increases so does the other)
draw the graph showing the effect of gas pressure on the rate of a reaction
rate of reaction on the y-axis
gas pressure on the x-axis
a straight line from the origin indicating that they are directly proportional (as one increases so does the other)
draw the graph showing the effect of surface are of solid reactants on the rate of a reaction
rate of reaction on the y-axis
surface are of solid reactants on the x-axis
a straight line from the origin indicating that they are directly proportional (as one increases so does the other)
define reversible reaction
once the products of the reaction have been made from the reactants, the products can react again to form the reactants
what is the forward and backward reaction in a reversible reaction
the forward reaction is when the reactants form the products and the backward reaction is when the products form the reactants
discuss the type of reactions in a reversible reaction
if the forward reaction is exothermic then the backward reaction will be endothermic and vice versa e.g. forward reaction: -82kJ then backward reaction: 82kJ
define a dynamic equilibrium
both the forward and backward reactions are taking place simultaneously and at exactly the same rate of reaction
what are the conditions required for a dynamic equilibrium?
the reversible reaction must take place in a closed system where no substances can get in or out
define what it means when an equilibrium lies to the left
it means there are more reactants than products in the mixture of chemicals at equilibrium
define what it means when an equilibrium lies somewhere in the middle
it means there is a similar amount of products and reactants in the mixture of chemical at equilibrium
define what it means when an equilibrium lies to the right
it means there are more products than reactants in the mixture of chemicals at equilibrium
what does le châtelier’s principle state?
if a change is made to the conditions of a system at equilibrium then the position of the equilibrium moves top oppose that change in conditions
discuss the effect of changing the concentration of a reactant on the position of the equilibrium
increasing the concentration means that the equilibrium will shift to the right to reduce the concentration
decreasing the concentration means that the equilibrium will shift to the left to increase the concentration
discuss the effect of changing the concentration of a product on the position of the equilibrium
increasing the concentration means that the equilibrium will shift to the left to reduce the concentration
decreasing the concentration means that the equilibrium will shift to the right to increase the concentration
discuss the effect of changing the temperature on the position of the equilibrium in a reaction where the forward reaction is exothermic
increasing the temperature means that the equilibrium will shift to the left (the endothermic direction) to lower the temperature
decreasing the temperature will move the equilibrium to the right (the exothermic direction) to increase the temperature
discuss the effect of changing the temperature on the position of the equilibrium in a reaction where the forward reaction is endothermic
increasing the temperature means that the equilibrium will shift to the right (the endothermic direction) to lower the temperature
decreasing the temperature will move the equilibrium to the left (the exothermic direction) to increase the temperature
discuss the effects of pressure on the position of the equilibrium when there are more reactant gas molecules than product ones
e.g. 2A(g) <—> B(g)
increasing the pressure will move the equilibrium to the right, the side with less gas molecules to reduce pressure
decreasing the pressure will more the equilibrium to the left, the side with more gas molecules to increase pressure
discuss the effects of pressure on the position of the equilibrium when there are more product gas molecules than reactant ones
e.g. A(g) <—> 2B(g)
increasing the pressure will move the equilibrium to the left, the side with less gas molecules to reduce pressure
decreasing the pressure will more the equilibrium to the right, the side with more gas molecules to increase pressure
do catalysts have an effect on the position of the equilibrium
it has no effect however it does increase the rate of forward and backward reactions, both by the same amount. this means that the system reaches equilibrium faster
