Calculating the equilibrium constant (Keq) Flashcards
What is the general equilibrium reaction represented by?
aA + bB ⇌ cC + dD
What is the formula for Keq given the general equilibrium reaction?
aA + bB ⇌ cC + dD
Keq = ( [C]^c * [D]^d) / ( [A]^a * [B]^b)
What do the square brackets [X] refer to?
Refers to the concentration of that substance in mol/L or M
What is the major rule for calculating Keq?
All solids and liquids are excluded from the equilibrium constant, thus, aqueous solutions and gases(if contained and molar volume can be measured) are only included
What is the reaction quotient; Q?
The left hand side of the Keq formula is commonly referred to as the reaaction quotient, Q, regardless of whether the reaction is in equilibrium or not
What happens if Q < K
Then the value of the numerator (concentration of products) is less, then reaction goes from the left to right until Q=k
What happens if Q = k?
The reaction is at equilibrium
What happens if Q > k
Then the value of thee denominator (concentration of the reactants) is less, then thee reaction goes from the right to the left until Q = k
Can the value of K give us info of the qualitative and quantitative information about position of equilibrium?
Yes
What does it mean if K is large (greater than 10^3)?
Equilibrium lies well to the right and favours the products
What does it mean if K is small (less than 10^-3)?
Equilibrium lies well to the left and favours the reactants
What happens if K has a ‘middle value’ (between 10^-3 and 10^3)?
At equilibrium three ill be appreciable concentrations of reactants and products (essentially in equilibrium)
How can Q and K be used to determine if a reaction is at equilibrium?
Value of K can be used to decide whether a particular reaction mixture is at equilibrium or not ( by comparing the value of the reaction quotient, Q, with the value of K)
