DrBob222
answered
mols HCl = M x L
Which is in excess. How much is the excess. If H in excess, (H^+) = mols/L solution. If OH in excess, ((OH^-) = mols/L. Then pH = -log(H^+) if H^+ is in excess. If OH is in excess it is pOH = -log(OH^-), the pH + pOH = pKw = 14. You will know pKw and pOH, solve for pH.
Explain Bot
answered
First, let's find the number of moles of potassium hydroxide (KOH) in 4.62 grams. We can do this by using the formula:
Number of moles = Mass (g) / Molar mass (g/mol)
The molar mass of KOH is calculated as follows:
Molar mass (KOH) = (atomic mass of K) + (atomic mass of O) + (atomic mass of H)
= (39.10 g/mol) + (16.00 g/mol) + (1.01 g/mol)
= 56.11 g/mol
Substituting the values into the formula:
Number of moles = 4.62 g / 56.11 g/mol
≈ 0.0824 mol
Since we mixed the potassium hydroxide in 1.00 L of water, the concentration of KOH in the solution is:
Concentration (KOH) = Number of moles / Volume (L)
= 0.0824 mol / 1.00 L
= 0.0824 M
Next, we need to determine the change in concentration of hydroxide ions after adding the 250.0 mL of 0.100 M HCl solution.
Using the equation:
Molarity (M) = Moles / Volume (L)
We can calculate the number of moles of HCl in the 250.0 mL solution:
Moles (HCl) = Molarity (HCl) * Volume (L)
= 0.100 mol/L * 0.250 L
= 0.0250 mol
Since HCl is a strong acid, it completely dissociates in water, forming one mole of H+ ions for every mole of HCl. Therefore, the change in concentration of hydroxide ions will be equal to the change in concentration of H+ ions.
In this case, the change in concentration of H+ ions is:
Change in concentration (H+) = - Moles (HCl)
= - 0.0250 mol
Now, let's calculate the concentration of hydroxide ions in the final solution:
Concentration (OH-) = [Initial concentration (KOH) - Change in concentration (H+)]
= [0.0824 M - (-0.0250 mol)]
= 0.0824 M + 0.0250 M
= 0.1074 M
Finally, to find the pH, we can use the formula:
pOH = -log (Concentration of hydroxide ions, [OH-])
pOH = -log (0.1074 M)
pOH ≈ 0.97
Since pH + pOH = 14 (at 25 degrees Celsius), we can calculate the pH as follows:
pH = 14 - pOH
= 14 - 0.97
≈ 13.03
Therefore, the resulting pH of the final mixture is approximately 13.03.
