We have this reaction :
HCO3- + OH- => CO3^-2 + H2O
Specify the conjugate pairs
and , which direction the reaction equilibrium shift ? and How ( as a rule ) ?
To determine the conjugate pairs in this reaction, we need to understand the concept of acids and bases.
An acid is a substance that donates a proton (H+), while a base is a substance that accepts a proton. In this reaction, HCO3- (bicarbonate ion) donates a proton, making it an acid, and OH- (hydroxide ion) accepts the proton, making it a base.
Conjugate pairs are formed when a substance loses or gains a proton. In this case, the conjugate acid of HCO3- is CO3^-2 (carbonate ion), which is formed when it loses a proton (H+). The conjugate base of OH- is H2O, which is formed when it gains a proton (H+).
So, the conjugate acid-base pairs in this reaction are:
Acid: HCO3-
Base: OH-
Conjugate acid: CO3^-2
Conjugate base: H2O
Now, let's discuss the direction in which the equilibrium of the reaction will shift. According to Le Chatelier's principle, a system at equilibrium will respond to a disturbance by shifting in a direction that minimizes the effect of the disturbance.
In this reaction, OH- accepts a proton to form H2O, and HCO3- donates a proton to form CO3^-2. So, by removing OH- (Base) or adding HCO3- (Acid), the equilibrium will shift to the left (reverse reaction). Conversely, by adding OH- or removing HCO3-, the equilibrium will shift to the right (forward reaction).
As a general rule, if you remove or decrease the concentration of a product or increase the concentration of a reactant, the equilibrium will shift in the forward direction to replace what has been removed. Conversely, if you increase the concentration of a product or remove a reactant, the equilibrium will shift in the reverse direction to replace what has been consumed.
Note: The equilibrium shift can also be influenced by changes in pressure and temperature, but in this reaction, we have not provided information about those factors.
In this reaction, the conjugate pairs are:
1. HCO3− and CO3^-2: HCO3− is the acid and CO3^-2 is its conjugate base.
2. OH− and H2O: OH− is the base and H2O is its conjugate acid.
To determine which direction the reaction equilibrium will shift, we need to consider a general rule known as Le Chatelier's principle. According to this principle, when a system at equilibrium is subjected to a stress, it will shift in a direction that minimizes the impact of the stress.
In this case, we have OH− and CO3^-2, which are both strong bases. The reaction involves the transfer of OH− from the base to the acid side. If we add more OH− to the system, the concentration of OH− will increase, causing a shift towards the acid side to minimize the impact of the increased OH− concentration. Therefore, the reaction equilibrium will shift to the left.
On the other hand, if we add more HCO3− (acid) to the system, the equilibrium will shift towards the right to minimize the impact of the increased acid concentration.
In summary, by adding OH−, the equilibrium shifts to the left, and by adding HCO3−, the equilibrium shifts to the right.
Why do you have the problem identifying the conjugate pairs?
The pair consists of the one with more H and the one with less H. And for CO3^2- it should be obvious not to pick H2O as its conjugate pair.