C8: Rates and equilibrium Flashcards
what does the rate of reaction tell us
how fast reactants turn into products
what are the two ways we can work out the rate of reaction
-find out how quick the reactants are used up as they make products
-find out how quick the products of the reaction are made
equation for mean rate of reaction
quantity of reactant used/product formed
DIVEDED BY
Time
four factors that affect rate of chemical reactions
-temperature
-surface area of solids
-concentration of solutions
-pressure of gases
-presence of a catalyst
what is collision theory
reactions can only take place when particles of reactants come together
what happens to the rate of reaction if you increase the SA:V
it also increases, as it increases frequency of collisions
why does temperature affect rate of reaction?
-particles collide with more energy
-particles collide more frequently
why does increased concentration in solutions have an affect on the rate of reaction
there are more particles moving in a set volume, so more collisions
why does increased pressure in gases have an affect on the rate of reaction
more particles in a given space, more collisions
what is a catalyst
a substance that speeds up a reaction without being used up itself
how do catalysts work
they offer an alternative reaction pathway that requires less energy (lower activation energy)
advantages of catalysts in industry
-cheaper than the possible energy
-more eco-friendly, burning less fuels
-can be used over and over again
con of catalysts in industry
-can become ‘poisoned’ in chemical plants, as impurites combine with it
what is reversible reaction
a reaction where the products can react together to make the original reactants again
how do we describe a reversible reaction within an equation
⇌
examples of reversible reactions
-litmus reacting to acid and alkali
-heating ammonium chloride
-reaction between iodine monochloride and chlorine gas
if a reversible reaction in 1 way is exothermic, it must be ______ the other way
endothermic
what is equal in the reversible reactions
the amount of energy in either way
what is equilibrium
the point where there is no change in the amount of products and reactants (both reacting at the same time)
what is Le Chatelier’s Principle?
whenever a change in condition is introduced to a change, the equilibrium shifts to cancel this out
what kind of changes can shift equilibrium
concentration, pressure and temperature
why do industrial chemists want to use le chatelier’s principle
to get as much products as possible, in as little time as possible
if the forward reaction produces more molecules of gas
-an increase in pressure decreases the amount of products
-a decrease in pressure increases the amount of products formed
if the forward reaction is exothermic…
-an increase in temperature decreases the amount of products formed
-a decrease in temperature increases the amount of products formed
