The Rate and Extent of Chemical Change Flashcards
(33 cards)
what is the rate of chemical reaction?
how fast the reactants are changed into products
what is collision theory?
the collision frequency of particles which transfers energy - the more collisions the faster the reaction is
what is the minimum amount of energy needed to start a reaction?
activation energy
why is activation energy needed?
to break the bonds in the reactants that start the reaction
what 4 things does rate of reaction depend on?
temperature, concentration of a solution/pressure of a gas, surface area and the presence of a catalyst
how does increasing the temperature increase the rate of reaction?
when the temperature is increased the particles will move faster meaning they will collide more frequently with more energy
how does increasing concentration/pressure increase rate of reaction?
if a solution is more concentrated it means there are more particles knocking about in the same volume or in a smaller space making collisions more frequent
how does increasing the surface area increase rate of reaction?
if one of the reactants is a solid then breaking it up into smaller pieces will increase the surface area to volume ratio meaning that the particles around the solid will have more area to work with so there will be more frequent collisions
how does using a catalyst increase rate of reaction?
they decrease activation energy by providing a different reaction pathway with a lower activation energy
how do you calculate rate of reaction?
amount of reactant used up or amount of product formed [divided by] time
how can you measure rate of reaction using precipitation and colour change?What experiment could you use this in?
observe a mark through the solution and measure how long it takes to disappear/how long a solution takes to lose or gain colour
sodium thiosulphate and hydrochloric acid produce cloudy precipitation
how can you measure rate of reaction using change in mass?
as a gas is released, the mass decreases - quicker decrease means faster rate
how can you measure rate of reaction using the volume of gas given off?What experiment could you use this for?
the more gas given off the quicker the reaction
magnesium and hydrochloric acid to produce hydrogen gas
what happens during a reversible reaction?
as the reactants react their concentrations fall so the forward reaction slows down but as more products are made and the concentration rises the backward reaction will speed up
when is a reversible reaction at equilibrium?
when the forward reaction is going at exactly the same rate as the backward one
what is happening to the reaction at equilibrium?
both reactions are still happening but there is no overall effect meaning the concentrations of the reactants and products have reached balance and wont change
what has to happen for equilibrium to be reached?
the system has to be closed
what is a closed system?
none of the reactants or products can escape and nothing can get in
what does it mean if the equilibrium lies to the right?
the concentration of products is greater than that of the reactants
what does it mean if the equilibrium lies to the left?
the concentration of reactants is greater than that of the products
what does the position of the equilibrium depend on?
the temperature, the pressure, the concentration of the reactants and products
what happens if the reversible reaction is endothermic in one direction?
it will be exothermic in the other and vice versa
what is the energy transferred from the surroundings during an endothermic reaction equal to?
the energy transferred to the surroundings during an exothermic reaction
what happens if you heat blue hydrated copper sulphate crystals?
it drives the water off and leaves white anhydrous copper sulphate powder
