Chemical Equilibrium Flashcards
When is a chemical reaction in equilibrium?
When the composition of the reactants and products remains constant indefinitely.
What does the value of equilibrium constant indicate?
The position of equilibrium.
What influences the numerical value of the equilibrium constant?
Reaction temperature, it is independent of concentration and/or pressure.
Influence on K for endothermic reactions
A rise in temperature causes an increase in K and the yield of the product is increased.
Influence on K for exothermic reactions
A rise in temperature causes a decrease in K and the yield of the product is decreased.
Does the presence of a catalyst affect the value of K
No
Amphoteric
Can react as an acid and a base
What is the value of the ionic product at 25 degrees Celsius?
1x10^-14
What are the concentrations of H30+ and OH^- at 25 degrees
10^-7 mol l^-1
Brønsted-Lowry definitions of acids and bases
State that an acid is a proton donor and a base is a proton acceptor.
Strong acids
Completely dissociated into ions in aqueous solution. Include: Hydorchloric acid, sulphuric acid, nitric acid.
Weak acids
Anything other than the three strong acids. Only dissociate partially into ions in aqueous solution. Sulfurous acid is a weak acid.
Strong bases
Solutions of metal hydroxides.
Weak bases
Ammonia and amines.
Buffer solution
One in which the pH remains approximately constant when small amounts of acid, base or water are added.
Acid buffer
Consists of a solution of a weak acid and one of its salts made from a strong base.
How does an acid buffer regulate pH?
The weak acid provides hydrogen ions when these are removed by the addition of small addition of a small amount of base. The salt of the weak acid provides the conjugate base, which can absorb excess hydrogen ions produced by the addition of a small amount of acid.
Basic buffer
Consists of a solution of a weak base and one of its salts.
How does a basic buffer regulate pH?
The weak base removes excess hydrogen ions, and the conjugate acid provided by the salt supplies hydrogen ions when these are removed.
Indicators
Weak acids. In aqueous solution the colour of an acid indicator is distinctly different from that of its conjugate base.
