topic 10 Flashcards
what is the symbol for a reversible reaction
—\
-–
what happenes in the forwards reaction of a reversible reaction
initially the reactants are used up quickley but then slows as their conc. drops
what happens in the backwards reaction of a reversible reaction
initially the reactants are reformed slowly then speed up as product conc. increases
what is dynamic equilibrium
rate of forwards reaction equals rate of backwards reaction in a closed system
what is le chateliers principle
if a reaction at equilibrium is subjected to change in pressure, temperature or concentration, the position of equilibrium will move to counteract change
what will happen to the position of equilibrium if concentration of reactants increase and concentration of products increase
increase conc, reactants = shift right
increase conc. products = shift left
what will happen to the position of equilibrium if pressure is increased
shift to the side with fewer moles of gas particles
what will happen to the position of equilibrium if temperature is increased and decreased
increased = shift to endothermic direction positve enthalpy change
decreased = shift to exothermic negative enthalpy change
what will happen to the position of equilibrium if a catalyst is used
no effect
speeds up rate of forwards and backwards equally
what is the equation for making ethanol
C2H4(g) + H2O (g) —> C2H5OH
AH = -46KJmol^-1
why is 300 degrees used when making ethanol
forwards reaction is exothermic
decreasing temp = shift right
lower temp means lower rate
compromise
why is a pressure of 60 atmospheres used when making ethanol
higher pressure = shift right and increase rate
high pressure expensive
compromise yield, speed and cost
what is a homogeneous reaction
all reactants and products in Kc as all gases/aq
write Kc expression for
2A + B –><— 2C + D
[A]^2 [B]
what is a heterogeneous reaction
dont include solids and pure liquids in final Kc as their conc. remain constant
