C6 rate and extent of chemical change Flashcards
(30 cards)
what is the formula to calculate the mean rate of reaction?
quantity of reactant used / time taken
on a rate graph, why does the line flatten out?
All the reactants has reacted so the reaction stops
on a rate graph. what does it mean when the line is steeper?
the steeper the line, the faster the reaction
how do you calculate the rate on a curved part of a line on a rate graph?
-pick a point
-draw a tangent
-make a triangle
-work out length of shorter sides
-use dy/dx to get the rate
why do chemical reactions happen (collision theory)?
reactant particles collide with enough energy (activation energy) to break the bonds between the reactant atoms (successful collisions)
if the pressure/concentration of the reactant is increased, why does the rate increase?
-there are more reacting particles in the same volume
-particles will collide more frequently
-more successful collisions
-so the rate increases
if the temperature of reactants is increased then why does the rate increase?
-higher temp so more energy
-particles move faster so they collide with more force/energy
-more frequent collisions
-more collisions with energy >= activation energy
-more frequent successful collisions
-so rate increases
if the surface area increases then why does the rate increase?
-more particles are exposed to the other reactant
-more frequent collisions per unit of time
-more successful collisions
-so the rate increases
what is the effect of a catalyst of rate
-a catalyst provides an alternative route for the reaction with a lower activation energy needed for a successful reaction
-but there are more successful collisions
-so the rate increases
describe a method to investigate the effect of the concentration of sodium thiosulfate on the rate of reaction (RP5)
what can the direction of reversible reactions be changed by?
changing conditions
what does dynamic mean
the forward and reverse reactions are both taking place at the same time
what do the conditions have to be like for dynamic equilibrium to occur
the reaction has to be in a closed system
in a closed system what is not possible to happen?
not possible for the products or reactants to escape the reaction vessel so there is no loss or gain in mass
how do you push the reaction to the products (right)?
by adding heat
how do you push the reaction to the reactants (left)?
by cooling it
what can be observed when copper sulphate is being heated?
-blue solid becomes white solid
-some steam is released
-test tube cools as heat is absorbed to break copper bonds
what can be observed when copper sulphate has been added water?
-white solid becomes blue solution
-test tube warms as heat is released due to formations of water bonds
what does le chatelier’s principle state?
if the conditions of an equilibrium are changed the position of the equilibrium moves to the oppose the change and re-establish the equilibrium
what does equilibrium mean?
at some point, the forward and the reverse reaction will take place at exactly the same rate
what happens if you increase temp in dynamic equilibrium?
shift to endothermic route, more product
what happens if you decrease temp in dynamic equilibrium?
shift exothermic, more reactant
what happens if you increase pressure in dynamic equilibrium?
shift to fewer mol side, more product
what happens if you increase pressure in dynamic equilibrium?
shift to higher mol, more reactant
