Equilibrium reactions, equilibrium calculations, the properties of water Flashcards
What is the rate of a chemical reaction?
Speed of change in concentration of reactants/products per unit time.
rate (mol L-1 s-1) = change measured / change in time
What does the gradient of the tangent to the curve on a conc vs time graph show?
Gives a measure of reaction rate
rate = y2-y1 / x2-x1
rate = change in conc^n / change in time
What factors influence a reaction rate?
- conc of reactants
- surface area
- temp
- catalysts
What is the relationship between rate and concentration?
rate α conc^n
What is K?
equilibrium constant
What is k1 and k2?
rate constants
What is K equal to?
Rate = k1[A][B] = K2[C][D]
K = [k2] / [k1] = [C][D] / [A][B]
What is the total pressure (PT) of a mixture of ideal gases equal to?
PT = PA + PB + PC + PD
What is the ideal gas equation?
PV = nRT
What is the relationship between the partial pressure and concentration of a gas?
PA α n
What is Kc?
molar concentration
What is Kp?
partial pressures
What are the two main purposes of Ks?
- magnitude of K
- predicting direction of a reaction
What can be the magnitude of K?
- large
- small
- around unity
What does a large magnitude of K imply?
> 10^2
reaction goes to ‘completion’
What does a small magnitude of K imply?
<10^-2
reaction ‘doesn’t occur’
What does a around unity magnitude of K imply?
100 - 0.01
all reactants present at equilibrium in significant quantities
What ‘stresses’ can you put on an equilibrium?
- change in concentration of reagent
- change in pressure of reaction
- change in temp of reaction
What is the Haber process?
N2 + 3H2 -> 2NH3
(ammonia)
What conditions does the Haber process have?
- high pressure (300 atm)
- low temp (≈ 450 °C)
What are the reaction conditions of the Haber process for Nitrogen Fixation?
- high pressure
- low temp
- remove NH3 as soon as formed
- catalyst
What does a catalyst do?
Increases rate of a reaction without undergoing any permanent chemical change.
How does a catalyst affect the equilibrium constant?
Does not alter the equilibrium constant
- allows equilibrium to be achieved more quickly
What are the effects of change in temp on an equilibrium?
- increase = favours endothermic reactions
- decrease = favours exothermic reactions
What is the Law of Mass Action?
When equilibrium is reached, reaction quotient (Q) = number that depends on:
- chemical reaction being considered
- temp of system
What is Q renamed as when reactions have reached equilibrium?
Q = K
