5.1.2 How Far? Flashcards
What is Kc
Equilibrium constant
Kc equation
mA + nB -> pC + qD
Kc = ([C]^p x [D]^q) all divided by ([A]^m x [B]^n)
Products/ reactants
How do you work out units for Kc?
Place units for each reactant/product into the equation and cancel out
Calculating moles at equilibrium
Moles of reactant= initial - moles reacted
Moles of products = initial moles + moles formed
Calculating Kc
Use MICE moles Initial change Equilibrium
Practical to work out equilibrium constant Kc
Ethanoic acid and ethanol reacted with sulfuric acid catalyst to make ethyl ethanoate
Stages to work out Kc in the practical
Work out initial amount of moles using mass density volume and then moles mass mr
Work out equilibrium moles of acid present from titre
Work out all equilibrium moles
Calculate Kc
Partial pressure definition
Pressure a gas would have alone if it occupied the volume occupied by the whole mixture
how do tou calculate partial pressure of a gas
Mole fraction x total pressure of gas
Mole fraction equation
number of moles of a gas divided by total number of moles of all gases
All partial pressures added together should equal what
Total pressure of gases
Kp
Equilibrium constant for gases
Using partial pressures
Products/ reactants
Kp expressions only contain what
Gaseous substances
Heterogeneous equilibria
What do Kc anx Kp change with
Temperature
Effect of temperature on Kc and Kp
Position of equilibria will change
Temp increased reaction favours endothermic
Shifts left
Kc decreases
Effect of concentration on Kc and Kp
Shift equilibrium but values dont change
Increases concentration moves equilibrium to right and increases other concentration
Restores equilibrium
Effect of catalysts on Kc and Kp
No effect
Speeds forwards and backwards reactions at same rate
Effect of pressure on Kc
Increased pressure reaction will shift to side with fewer moles of gas
Shifts right
Kc stays same
Increases conc on bottom of equation so top increases and bottom decreases to restore values
Effect of pressure on Kp
Kp stays constant
Increases pressure on bottom of equation so shifts right to increase mole fraction of products to decrease mole fraction of reactants
Kp is restored
