What is the pH of the solution created by combining 2.20 mL of the 0.10 M NaOH(aq) with 8.00 mL of the 0.10 M HCl(aq)? with 8.00 mL of the 0.10 M HC2H3O2(aq)?
To find the pH of a solution, we need to determine the concentration of H+ ions in the solution. H+ ions are responsible for the acidic properties of a solution.
First, let's determine the number of moles of H+ ions in each case.
For the reaction between NaOH and HCl:
1. Calculate the number of moles of NaOH:
Moles = volume (in L) x concentration
Moles of NaOH = 2.20 mL x (1 L / 1000 mL) x 0.10 M = 0.00220 mol
2. Since NaOH is a strong base, it completely dissociates in water to yield one mole of OH- ions for every mole of NaOH. Therefore, the concentration of OH- ions is also 0.00220 M.
3. Calculate the number of moles of HCl:
Moles of HCl = 8.00 mL x (1 L / 1000 mL) x 0.10 M = 0.00800 mol
4. Since HCl is a strong acid, it completely dissociates in water to yield one mole of H+ ions for every mole of HCl. Therefore, the concentration of H+ ions is also 0.00800 M.
5. To find the overall concentration of H+ ions, we subtract the concentration of OH- ions from the concentration of H+ ions since they will react and neutralize each other:
Overall concentration of H+ ions = 0.00800 M - 0.00220 M = 0.00580 M
Now, let's consider the reaction between NaOH and HC2H3O2:
1. Calculate the number of moles of NaOH:
Moles of NaOH = 2.20 mL x (1 L / 1000 mL) x 0.10 M = 0.00220 mol
2. As mentioned before, the concentration of OH- ions is also 0.00220 M.
3. Calculate the number of moles of HC2H3O2:
Moles of HC2H3O2 = 8.00 mL x (1 L / 1000 mL) x 0.10 M = 0.00800 mol
4. HC2H3O2 is a weak acid, so it does not fully dissociate. However, it does partially dissociate to yield some H+ ions and acetate (C2H3O2-) ions. The concentration of H+ ions is determined by the extent of dissociation of HC2H3O2, which we can calculate using the acid dissociation constant (Ka) of HC2H3O2.
5. The Ka value for HC2H3O2 is 1.8 x 10^-5. We can use this value to calculate the concentration of H+ ions. Let's assume x is the concentration of H+ ions from the dissociation of HC2H3O2. Then, the concentration of acetate ions (C2H3O2-) is also x. The concentration of HC2H3O2 remaining is 0.00800 - x.
Ka = [H+][C2H3O2-] / [HC2H3O2] = (x)(x) / (0.00800 - x)
Solve this quadratic equation to find the concentration of H+ ions. In this case, the concentration of H+ ions is approximately 0.008 M.
Finally, to find the pH:
pH = -log[H+]
pH = -log(0.00580) ≈ 2.24 (for the solution with HCl)
pH = -log(0.008) ≈ 2.10 (for the solution with HC2H3O2)
Therefore, the pH of the solution created by combining 2.20 mL of the 0.10 M NaOH(aq) with 8.00 mL of the 0.10 M HCl(aq) is approximately 2.24, and the pH of the solution created by combining 2.20 mL of the 0.10 M NaOH(aq) with 8.00 mL of the 0.10 M HC2H3O2(aq) is approximately 2.10.