Topic 2-energetics Flashcards
What is an endothermic reaction
A reaction which converts heat energy into chemical energy to break bonds causing the temp of surroundings to drop. Reactants have less energy than products and /\H = positive
What is an exothermic reaction
A reaction which converts chemical energy into heat energy when making new bonds causing the surroundings temp to rise. Reactants have more energy than products and /\H = negative
What is a reversible reaction
A reaction where the products can react to produce the original reactants again
Dynamic equilibrium ?
It is dynamic in the sense that it is still occurring and equilibrium in the sense that the total amounts of all the things present are now constant , can only occur in closed conditions
What are closed conditions
No substances can be added or escape from the reaction
Example of reversible reaction?
Anhydrous copper (II) sulphate + H20—> hydrated copper (II) sulphate
White solid turns blue in the presence of water
What is le chateliers principle
If a dynamic equilibrium is disturbed by changing conditions the reaction will move to counteract that change .
What things can be done to influence a dynamic equilibrium
Change temp
Change pressure
Change concentration
Add a catalyst
How would changing pressure affect the reaction if there are the same number of molecules on each side of the equation
Only applies to gas reactions where the total number of molecules on each side of the equation Are different if therre are the same number of molecules on each side of the equilibrium, changing pressure won’t make a difference to equilibriums position
What will an increase in pressure do if thee are more molecules on one side of the equation?
Inc. in pressure will lead to more of the side with less molecules being made as the reaction wil move to counteract tithe increase in pressure by producing fewer molecules to hit the container and therefore decrease the pressure
Vice versa for decrease in pressure
What would a change in concentration do to the position of the equilibrium ?
Only applies to reaction with solutions
an increase in the concentration of a substance tips the equilibrium in the direction that decreases the concentration of the substance added in order to counteract that change
Changing temperature
An inc in temp will cause the reaction to move to counteract this change by favouring the endothermic reaction and absorbing the extra heat in endothermic change
A decrease in temp will cause the reaction to move to counteract its change by inc the temp again through exothermic change
How would adding a catalyst influence a dynamic equilibrium
Makes no difference to position of equilibrium
Speeds up the rate at which equilibrium is reached and speeds up the backwards and forwards reactions by the same amount
