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
To determine the pH of the solution, we need to understand the neutralization reaction and the properties of the compounds involved.
Na2HPO4 is a salt formed from the reaction between NaOH (a strong base) and H3PO4 (a weak acid). It is a weak base itself because the sodium ion does not have any acidic or basic properties.
When a strong acid is added to a solution containing Na2HPO4, it reacts with the weak base Na2HPO4 to form a new salt and water. The reaction can be written as follows:
H+ (strong acid) + HPO4^2- (weak base) → H2PO4^- (new salt) + H2O
In this case, we are adding sufficient strong acid to neutralize one-half of the Na2HPO4. This implies that the moles of strong acid added are equal to half of the moles of Na2HPO4 in the solution.
Now, let's consider the pH of the solution after the neutralization reaction. Since H2PO4^- is the conjugate base of H3PO4 (a weak acid), we can assume that it will still have some acidic properties. As a result, the solution will be acidic.
To calculate the pH, we need to consider the equilibrium of the water molecule.
H2O ⇌ H+ + OH-
The concentration of H+ ions in water is 1.0 x 10^-7 mol/L, and the concentration of OH- ions is also 1.0 x 10^-7 mol/L due to the auto-ionization of water.
Since H2O is a reactant in the neutralization reaction, it is consumed when it reacts with the strong acid that was added. This means that the concentration of OH- ions in the solution decreases, resulting in an increase in the concentration of H+ ions.
Therefore, the pH of the solution decreases, indicating that it becomes more acidic. However, without knowing the specific strong acid that was added or the concentration of Na2HPO4, it is not possible to determine the exact pH value.
In summary, when a sufficient amount of strong acid is added to a solution containing Na2HPO4 to neutralize one-half of it, the resulting solution will become more acidic. The exact pH value depends on the specific strong acid added and the concentration of Na2HPO4.