2.1a Equilibrium constant and the ionic product of water Flashcards
What is a chemical reaction in equilibrium?
when the composition of the reactants and products remain constant indefinitely
What does the equilibrium constant (K) characterise?
the composition of the reaction mixture
What is the equilibrium expression for the general reaction:
aA+bB=cC+dD
k=[C]^c[D]^d/[A]^a[B]^b
What are [A] , [B], [C] and [D]?
the equilibrium concentrations of A, B, C and D
what are a, b, c and d?
the stoichiometric coefficients in the balanced reaction equation
What does the value of the equilibrium constant indicate?
the position of equilibrium
What happens to pure solids and pure liquids when writing an equilibrium expression?
the concentrations of pure solids and pure liquids at equilibrium and taken as constant and given a value of 1
What does the value of the equilibrium constant depend on?
the reaction temperature
What does the value of the equilibrium constant not depend on?
-concentration
-pressure
For endothermic reactions what does a rise in temperature cause
-increase in K
-yield of the product is increased
For exothermic reactions what does a rise in temperature cause?
-decrease in K
-yield of the product is decreased
What effect does a catalyst have on the equilibrium constant?
no effect
What is there an equilibrium between in water?
water molecules and hydronium(hydrogen) and hydroxide ions
What equation can the ionisation of water be represented by?
H2O(l)+H2O(l)=H3O+(aq)+OH-(aq)
What is the hydronium ion?
-H3O+(aq)
-hydrated proton
-short hand way H+(aq)
What substance is amphoteric?
water
What does amphoteric mean?
it can react as an acid or a base
What is the dissociation constant for the ionisation of water also known as?
the ionic product
What can Kw be represented by?
Kw=[H3O+][OH-]
what can alter the value of the ionic product?
temperature
what is the value of Kw at 25*C (298K)
1x10^-14
Give two expressions for the relationship between pH and hydrogen ion concentration
-pH=-log10[H3O+]
-[H3O+]=10^-pH
What happens in relation to ion concentration at pH 7?
the concentrations of H3O+(aq) and OH-(aq) are both 10^-7moll^-1 at 25*C (298K)
Give an equation for when the concentration of H3O+(aq) or OH-(aq) is known and you would like to work out the other
pH + pOH = 14
