Equilibrium Flashcards
Reversible Reaction
Is one in which the products, once made, can react to reform the reactants.
Closed and Open system
Closed system- No substances can get in or out
Open system- Allows entry and exit of substances
Lá Chateliers Principle
Conditions of a system at equilibrium is changed, position of equilibrium moves to oppose that change and undo the effects that where changed
Dynamic Equilibrium
Occurs in a closed system, when the rates of the forward and reverse reactions are equal, amounts of reactants and products remain constant.
Homogeneous
All reactants and products are in the same state
Effect of changing the concentration - how position of equilibrium changes
Increase concentration of a reactant = moves right to reduce concentration of reactant
Decrease concentration of a reactant = moves left to reduce concentration of reactant
Increase concentration of a product = moves right to reduce concentration of product
Decrease concentration of a product = moves left to reduce concentration of product
Effect of changing the temperature
Forward reaction exothermic- increase of temp, equilibrium position moves left in endothermic direction as to lower the temp. Decrease in temp, equilibrium moves right in exothermic direction to increase the temp. Forward reaction endothermic- increase of temp, equilibrium position moves right in endothermic direction as to lower the temp. Decrease in temp, equilibrium moves left in exothermic direction to increase the temp.
Effect of changing the pressure
2A -> B- increase in pressure, equilibrium moves to the right, with fewer molecules or decrease the pressure. Decrease in pressure, equilibrium moves to the left with more molecules to increase the pressure.
A -> B - Equilibrium position doesn’t move as no of molecules is equal
A + B -> 4C - increase in pressure, equilibrium position moves left to side with fewer molecules as to decrease pressure. Decrease in pressure, equilibrium position moves right to side with more molecules as to increase pressure.
Haber process
Combines nitrogen from air with hydrogen into ammonia. Is a exothermic reaction. N2(g) + 3H2(g) —> 2NH3
Conditions in Haber process
Pressure- 200atm, Temperature- 450degrees Celsius, Iron catalyst
Temperature gives a high yield of ammonia. Why? What is 450 degrees used?
Ammonia produced by forward exothermic reaction. Decrease in temp- equilibrium moves to the right in the exothermic direction, to reduce the temp, so more ammonia produced. Although a low temp produces a high yield- reaction is too slow and a comprise temp is 450 degrees Celsius as to produce a reasonable yield of ammonia.
Catalyst has no effect on yield of ammonia. Why?
A catalyst only speeds up the rate of reaction, no effect on equilibrium so no effect on yield of ammonia
Why does a high pressure give a high yield of ammonia. Why is only 200atm uses
High pressure used equilibrium position moves right, side with fewer gas molecules, to decrease pressure so more ammonia is produced. However a large amount of energy is needed to compress the gases, and the thick pipes with valves are expensive. So comprise is met.
