Influence of pressure
The pressure of a gas is associated with the volume of this gas. Increasing pressure benefits the lower volume reaction and decreasing pressure benefits the higher volume reaction.
Gas volume increase = EXPANSION
Gas volume decrease = CONTRACTION
Be the chemical reaction:
The volume occupied by conductors and products follows the stoichiometric ratio. In this case, the product has lower volume. With increasing pressure, the balance will shift to the right direction, because it has less volume.
Pressure increase = EQ for smaller volume side
Pressure Decrease = EQ for higher volume side
For these changes, there is no change in the KC value.
Influence of temperature
It is the only change that can modify the value of KC.
Increasing temperature benefits the endothermic reaction.
Decreasing temperature benefits the exothermic reaction.
The presence of a catalyst (chemical that accelerates the chemical reaction) does not change the KC value. The catalyst promotes a decrease in the moment of equilibrium. Changes in both direct reaction and reverse reaction.
Chemical Equilibrium Displacement Summary
Kc or Kp change
Adding a participant
In the opposite direction to the participant
Withdrawal from a Participant
In the sense of the participant
Increased total pressure
Toward the smallest volume
Total pressure decrease
Toward the highest volume
In the endothermic sense
In the exothermic sense
Chemical Balance - 2
Acidity constant (Ka) and basicity constant (Kb)
When an acid comes into contact with water, we say that an ionization has occurred. For the bases, we use the term dissociation. Here's what happens when hydrochloric acid is added in water:
Its equilibrium constant is given by:
Note that the liquid substance water should not participate in the equilibrium constant because its concentration is constant. So if the water concentration is multiplied by KC, we get a new constant, the acidity constant, Ka.
The acidity constant indicates the strength of the acid. The lower the Ka value, the weaker the acid. Less ionized is this acid. This constant is used for weak acids. Strong acids have no Ka, as they dissociate completely and have no balance (direct and inverse reaction).
The acidity constant is linked to the degree of ionization of an acid.
The higher the Ka, the greater the degree of ionization, hence strong acid.
The lower the Ka, the lower the degree of ionization, thus weak acid.
Look at the table of acids with different Ka values and their acid strength:
Ka (25 ° C)
We can also use to demonstrate the value of the acidity constant, the ionization constant, Ki.
THE basicity constant is given by Kb, and indicates the strength of the base and its degree of dissociation. It is similar to Ka, but now it refers to the bases.