Chemical equilibria, Le chatelier's principle, Kc Flashcards
How is dynamic equilibrium formed ?
At the start of the reaction the forwards reaction is fast and the backwards reaction is slow.
After the start the reverse reaction speeds up as the forward reaction slows down,
Until the rates of both reactions are the same.
What does dynamic mean ?
The forward and backward reactions proceed at equal rates.
What does equilibrium mean ?
The concentration of the reactants and products are the same.
What is le chatelier’s principle ?
The position of equilibrium will shift to oppose a change made to it.
What happens if the concentration of the reactants increases ?
equilibrium will shift to the right to oppose the addition of reactants so yield of products increases.
What happens if the concentration of reactants decreases ?
equilibrium will shift to the right to oppose the removal of reactants so the yield of reactants will increase.
2NO2 <-> N2O4
What will happen if pressure is increased ?
More moles on the left so equilibrium shifts to the right to oppose increase in pressure so yield of N2O4 increases.
2NO2 <-> N2O4
What will happen if pressure is decreased ?
More moles on the left so equilibrium shifts to the left to oppose decrease in pressure so yield of NO2 increases.
What is the relationship between pressure and volume ?
inversely proportional ( as v increases p decreases)
CH4 + H2O <-> CO + 3H2
D H = -206
What will happen if temperature decreases ?
forward reaction is exothermic, equil shifts to the right to oppose decrease in temperature so yield of products increases.
CH4 + H2O <-> CO + 3H2
D H = -206
What will happen if temperature increases ?
backwards reaction is endothermic so equil shifts to the left to oppose increase in temp so yield of reactants increases.
What is a catalyst ?
A substance that speeds up the rate of reaction without being used up.
What happens when a catalyst is added to a reversible reaction ?
The rate of the forwards and backward reactions increase equally so there is no change in the position of equilibrium.
Why are compromise conditions used in the haber process ?
HIgh pressure gives high yield but expensive
low temp gives high yield but rate of reaction will be too low.
Write an expression for kc.
Kc = [PROD]/[REACT]
