Write two reactions for NaHCO3, reacting with water in one NaHCO3 is acting as acid the other as a base. Is 0.10M solution going to be acidic or basic? Explain.
I write the two rxns but what do I do with then...
You may be expected to derive the equation for calculating the pH of a 0.1M soln of NaHO3. The shortcut equation is
(H^+) = sqrt(k1k2) or pH =1/2(pK1 + pK2)
To determine whether a 0.10M solution of NaHCO3 is acidic or basic, we need to analyze the reactions that occur when NaHCO3 reacts with water, considering NaHCO3 as an acid in one reaction and as a base in the other.
1. NaHCO3 acting as an acid:
When NaHCO3 acts as an acid, it donates a proton (H+) to the water molecule, resulting in the formation of bicarbonate ion (HCO3-) and hydronium ion (H3O+).
The reaction can be represented as follows:
NaHCO3 + H2O ⟶ HCO3- + H3O+
2. NaHCO3 acting as a base:
When NaHCO3 acts as a base, it accepts a proton (H+) from the water molecule, leading to the formation of carbonate ion (CO3^2-) and hydroxide ion (OH-).
The reaction can be represented as follows:
NaHCO3 + H2O ⟶ CO3^2- + OH-
Now, to determine if the 0.10M NaHCO3 solution is acidic or basic, we need to consider the concentration of hydronium ions (H3O+) or hydroxide ions (OH-) in the solution.
In the first reaction, the formation of H3O+ indicates acidity, while in the second reaction, the formation of OH- indicates basicity.
However, it's important to remember that NaHCO3 is a weak acid and a weak base. Consequently, the extent of ionization of NaHCO3 is relatively small. To make an accurate determination, we need to consider the dissociation constants of the acidic and basic reactions of NaHCO3.
The Ka (acid dissociation constant) for the acid reaction is approximately 4.7 x 10^-11, indicating that the acidic dissociation is very weak. On the other hand, the Kb (base dissociation constant) for the base reaction is very small, given that the base dissociation of NaHCO3 is even weaker.
Considering these dissociation constants and the fact that NaHCO3 is a relatively weak acid and base, we can conclude that the 0.10M solution of NaHCO3 will be slightly basic due to the formation of a small amount of OH- ions.
Therefore, the 0.10M NaHCO3 solution is expected to be slightly basic.