What is the pH at the equivalence point in the titration of 0.250 M HX (Ka = 5.2 x 10^-6) with 0.250 M KOH?
To find the pH at the equivalence point in this titration, we need to consider the stoichiometry of the reactants as well as the dissociation of the acid, HX.
The reaction between HX and KOH can be written as follows:
HX + KOH -> H2O + KX
At the equivalence point, the moles of HX will be exactly neutralized by the moles of KOH. Therefore, we need to determine the volume of KOH required to neutralize the HX.
To do this, we can use the balanced equation and the initial concentrations of HX and KOH. Since the initial concentrations of both HX and KOH are 0.250 M, the moles of HX initially present can be calculated by multiplying its initial concentration by its volume (let's call it VHX).
Next, we note that the stoichiometry of the reaction tells us that 1 mole of HX reacts with 1 mole of KOH. Therefore, the moles of KOH required to neutralize the HX will be equal to the moles of HX initially present.
Once we have determined the moles of KOH required, we can convert it to volume (let's call it VKOH) using the initial concentration of KOH.
Now that we have determined the volume of KOH required to reach the equivalence point (VKOH), we can calculate the moles of HX that remain after the neutralization.
Since the initial moles of HX were equal to its initial concentration times its volume (moles = concentration x volume), the moles of HX remaining after neutralization will be equal to the initial moles of HX (molesHXinitial) minus the moles of KOH used (molesKOHused).
Finally, we can calculate the concentration of HX remaining after neutralization (HXR) by dividing the moles of HX remaining after neutralization by the total volume of the solution.
To find the pH at the equivalence point, we need to use the dissociation constant of HX, Ka = 5.2 x 10^-6.
The dissociation constant, Ka, can be used to calculate the concentration of H+ ions in a solution of HX. At equilibrium, the concentration of H+ ions will be equal to the square root of (Ka times HXR).
Using this concentration of H+ ions, we can now calculate the pH by taking the negative logarithm (base 10) of the concentration of H+ ions.
By following these steps, you should be able to determine the pH at the equivalence point in the titration of 0.250 M HX with 0.250 M KOH.