Equilibrium & atom economy Flashcards
(20 cards)
What are the three features of dynamic equilibrium?
- forward and reverse reactions are both happening at the same rate
- so the concentration of each substance is staying constant
- happens in a closed system
Draw a graph where the equilibrium position is to the right
Draw a graph where the equilibrium position is to the left
What does it mean in terms of quantities of products and reactants when the equiblib position is to the right?
more products are produced then reactants
What does it mean in terms of quantities of products and reactants when the equiblib position is to the left?
more reactants are produced than products
state le chatelier’s principle
if a reaction is at equilibrium and then a change is made in any of the conditions (temp, pressure, concentration, etc) then the position of equilibrium will shift in the direction that minimises the change
how would increasing the pressure shift the equibilirium position?
increasing the pressure would shift the equilibrium position in the direction with fewer gas molecules (they take up less space so reduce the pressure, minimising the change)
how would increasing the temperature shift the equilibrium position?
increasing the temperature would shift the equilibrium position in the endothermic direction (this takes heat in, reducing the temperature, so minimising the change)
how would changing the concentration shift the equilibrium position?
if the concentration of one reactant or product is increased, the equilibrium shifts away from it in order to use up the extra prod/react.s so minimising the change
how would adding a catalyst shift the equilibrium position?
a catalyst does not alter the position of equilibrium, this is because the catalyst speeds up the rate of both the forwards and reverse reactions equally. but the reaction will reach equilibrium quicker
what 4 points should you include when answering an equilibrium question?
- which way the equilibrium position shifts
- why (e.g: more moles/reverse reaction is endothermic)
- this will minimise the change
- (if asked) comment of yeild of product or composition of mixture
What is the only thing that alters the Kc value?
temperature
what does it mean when the value of Kc > 1?
more products than reactants are produced at equilibrium
what does it mean when the value of Kc > 10^10?
equilibrium far on the right, the reaction appears to have gone to completion
what does it mean when the value of Kc < 1?
more reactants than products are produced at equilibrium
what does it mean when the value of Kc < 10^-10?
equilibrium far on the left, the reaction appears not to have happened
what does it mean when the value of Kc is close to 1?
there are similar amounts of reactants and products at equilibrium
how are Kc value and le chatelier’s principle connected?
the composition of the mixture will always adjust to keep the value of Kc constant (unless temp changes)
what is atom economy? what does high atom economy mean?
a measure of the proportion of reactants that are converted into useful products in the equation. high atom economy means less waste
what’s the formula for atom economy?
% atom economy = Mr of useful product/total Mr of all products x 100
