The rate and extent of chemical change Flashcards
what is the rate of chemical reaction mean?
how fast the reactants are changed into products.
Example of slow rate of reaction ?
rusting of iron , chemical weathering
Example of moderate rate of reaction?
magneusium reaction with an acid to produce a gentle stream of bubbles.
Example of a fast rate of reaction?
Burning, explosions
Graphs for rate of reaction
Page 67
What is the collision theory?
the more collisions there are the faster the reaction is.E.g doubling the frequency of collisions doubles the rate.
the energy transferred during a collision.Particles have to collide with enough energy for the collision to be successful.
What are the four things the rate of reaction depends on?
temperature
the concentration of a solution or pressure of a gas
surface area
the presence of a catalyst
How does increasing temperature incrase rate of reaction?
when the temp is increased, the particles will move faster.If moving faster, they collide more frequently.also the faster they move the more energy they have, so more of the coillisions will have enough energy to make the reaction happen
How does increasing the concentration or pressure increase the rate of reaction?
if a solution is made more concentrated, it means there are more particles knocking about in the same volume of water.(or other solvent).This makes collisions between the reactant particles more frequent.
How does increasing the surface area increase the rate of reaction?
if one reactant is a solid, then breaking it up into smaller pieces will increase its sufrace area to volume ratio.
this means that for the same volume of the solid, the particles around it will have more area to work on - so there will be collisions more frequently.
How does using a catalyst increase the rate of reaction?
they do this by providing an alternative reaction pathway with a lower activation energy .Enzymes are biological catalysts - they catalyse reactions in living things.
How to work out mean of reaction rate from graph page 71
71
Draw a tangent to find the reaction rate at a particular point. page 71 bottom
71 bottom
what is a reversible reaction?
as more and more products are made their concentrations rise, the backward reaction will speed up.Eventually the forward reaction will go at the same rate as the backward reaction - the system is at equilbrium.
What does the position of the equilibrium show.
if to the left, the concentration of products is greater than that of the reactants
if to the right,the concentration of reactants is greater than that of the products
What determines what side the position of equilibrium is?
temp
the pressure
concentration
Is a reversible reaction endothermic or exothermic?
if the reaction is endothermic in one direction, it will be exothermic in the other.
What is Le Chatelier’s principle?
the idea that if u change the conditions of a revcersible reaction at equilbrium, the system will try to counteract that change.
can be used to predict the effect of any changes you make to a reaction system.
How does temeperature determine the position of Equilibrium?
If you decrease the temperature, the equilibrium will move in the exothermic direction to produce more heat.
If you raise the temperature , the equilibrium will move in the endothermic direction to try and decrease it .
How does the pressure determine the position of Equilibrium?
only affects when involving gases
If increase pressure, equil tries to reduce it, moves to direction with fewer molecules of gas
If decrease pressure, equil tries to increase it,move to direction with more molecules of gas.
How does concentration determine the position of Equilibrium?
If you increase the concentration of reactants,system tries to decrease it by making more products
If you decrease the concentration of products, systen tries to increase it again by reducing the amount of reactants.
Chem-skl
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What is the mean rate of reaction is equal to?
quantity of reactant used time taken
Or
quantity of product formed time taken
What are the quantities of reactants or products measured in?
The quantities can be mass in grams or volume cm^3
