Equiibria and Kc
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What is meant by dynamic equilibrium?
• rate of forward reaction = rate of backwards reaction • concentrations of reactants and products constant
Give a reason why a high pressure of 50 MPa is not normally used in the Haber Process
Too expensive to generate
State and explain, by using Le Chatelier’s principle, one advantage, other than cost, of using a temperature lower than 800 K
Yield of ammonia increases (1) Exothermic reaction favoured (1) System moves to raise temp / or oppose decrease in temp (1)
Why is 800K a compromise temperature?
Balance between rate and yield (1)
Kc for this equilibrium has no units. State why the units cancel in the expression for Kc
equal number of moles
use le chatelier’s principle to explain if high/low temp should be used to obtain highest possible yield of hydrogen. CH4 + H2O —> CO + 3H2 enthalpy change = +206kj mol-1
• high temperature • forward reaction = endothermic • at high temperatures equilibrium shifts to the right
explain in terms of particles why high operating pressure is used in industry
• increases rate of reaction • higher pressure = higher concentration of particles • so more collisions
nickel catalyst is used. explain why catalyst is more effective when coated onto an unreactive honeycomb
• increase in surface area • so more successful collisions
The total volume of the mixture does not need to be measured to allow a correct Kc value to be calculated. justify this statement
volume cancels out/equal number of moles on each side