Sufficient strong acid is added to a solution containing Na2HPO4 to neutralize one-half of it. what will be the pH of this solution? Explain please
pH = pKa2 + log (base/acid)
HPO4^2- + H^+ ==> H2PO4^-
Suppose you start with any amount of HPO4^2- (let's say 10 moles). If you add H^+ to neutralize 1/2 of it, then you will have 5 moles H2PO4^- formed and 5 moles HPO4^2- left un-neutralized.
Plug into the HH equation, first line, base = acid so that fraction is 1.0, log 1.0 is zero so pH = pKa2.
There are 3Ka values for H3PO4. k1 is for mixtures of H3PO4 and H2PO4^-; k2 is for mixtures of H2PO4^- and HPO4^2- (which is what is in the problem); k3 is for mixtures of HPO4^2- and PO4^3-
Well, if you're trying to neutralize one-half of the Na2HPO4, you should probably be prepared for some salty reactions. But fear not, I'm here to clarify things for you in a clownish yet informative manner!
Na2HPO4 is a sodium phosphate compound that contains basic PO4(3-) ions. Adding a strong acid will react with these basic ions, resulting in the formation of H2PO4(-) ions. Now, since you're only neutralizing one-half of the Na2HPO4, you'll have an equal concentration of H2PO4(-) and PO4(3-) ions remaining in the solution.
The pH of a solution depends on the concentration of H+ ions, and since H2PO4(-) can act as a weak acid by donating H+ ions, it will slightly increase the acidity of the solution. However, PO4(3-) does not contribute to the H+ concentration or affect pH much.
Therefore, the ultimate pH of the solution will be slightly acidic, due to the presence and partial dissociation of H2PO4(-).
But keep in mind, this explanation is just a clown's perspective on the matter. For precise calculations or deeper understanding, it's always recommended to consult a chemistry professional or textbook.
To determine the pH of a solution, we need to understand the nature of the chemical components in the system and their acid-base properties.
The compound Na2HPO4 (sodium hydrogen phosphate) is a salt derived from a weak acid (H3PO4, phosphoric acid) and a strong base (NaOH, sodium hydroxide). When dissolved in water, Na2HPO4 dissociates into its respective ions:
Na2HPO4 → 2Na+ + HPO4 2-
The HPO4 2- ion can act as a weak base by accepting a proton (H+) from the solution:
HPO4 2- + H2O ⇌ H2PO4 - + OH-
Since a sufficient strong acid is added to neutralize half of the Na2HPO4, it means that half of the HPO4 2- ions are converted into the conjugate acid, H2PO4 -.
HPO4 2- + H+ → H2PO4 -
This reaction results in the formation of H2PO4 - ions and a corresponding quantity of H+ ions. The H2PO4 - ion is the conjugate acid of HPO4 2- and possesses acidic properties.
Now, we can consider the pH of the solution. The pH scale measures the concentration of H+ ions in a solution. It is calculated from the negative logarithm of the H+ concentration.
pH = -log[H+]
Since only half of the HPO4 2- ions are neutralized, the number of H+ ions formed is also halved. Therefore, the concentration of H+ ions in the solution is reduced by a factor of 2. In terms of pH, this means that the pH decreases by 0.3 units.
For example, if the original pH of the Na2HPO4 solution was 7, it would decrease to approximately pH 6.7 after the addition of the strong acid, as the H+ concentration doubles.
Thus, the pH of the solution will decrease by 0.3 units after sufficient strong acid is added to neutralize half of the Na2HPO4 ions.