How do i calculate the pH when 200ml of .200M HCl is added .4998M of sodium acetate?
To calculate the pH of a solution, you need to consider the dissociation of the acids and bases present in the solution. In this case, you have HCl, which is a strong acid, and sodium acetate, which is the conjugate base of a weak acid (acetic acid).
To calculate the pH, follow these steps:
Step 1: Determine the initial concentrations of the acid and base in the solution. You are given that the initial concentration of HCl is 0.200 M, and the concentration of sodium acetate is 0.4998 M.
Step 2: Determine the moles of HCl and sodium acetate present in the solution. Moles can be calculated by multiplying the concentration (M) by the volume (L) of the solution. In this case, the volume of the solution is 200 mL or 0.200 L.
Moles of HCl = concentration of HCl (mol/L) × volume of solution (L) = 0.200 mol/L × 0.200 L = 0.040 mol
Moles of sodium acetate = concentration of sodium acetate (mol/L) × volume of solution (L) = 0.4998 mol/L × 0.200 L = 0.09996 mol
Step 3: Determine the moles of the excess base or acid formed after the reaction. In this case, HCl is a strong acid and will fully dissociate, while sodium acetate will partially ionize. The balanced chemical equation for the reaction between HCl and sodium acetate is:
HCl + CH3COONa -> CH3COOH + NaCl
Since HCl is a strong acid, it will dissociate completely into H+ and Cl- ions. Therefore, the moles of excess base formed will be equal to the initial moles of sodium acetate.
Moles of excess base = moles of sodium acetate = 0.09996 mol
Step 4: Determine the moles of the remaining acid or base in the solution after the reaction. In this case, HCl will be fully consumed in the reaction, so the moles of remaining acid will be zero.
Moles of remaining acid = 0 mol
Step 5: Determine the moles of the resulting acid or base formed after the reaction. In this case, the reaction between HCl and sodium acetate forms acetic acid (CH3COOH). The moles of the resulting acid will be equal to the moles of excess base formed.
Moles of resulting acid = moles of excess base = 0.09996 mol
Step 6: Calculate the concentration of the resulting acid or base. Concentration can be calculated by dividing the moles by the volume of the solution. In this case, the volume of the solution is still 0.200 L.
Concentration of resulting acid = moles of resulting acid / volume of solution = 0.09996 mol / 0.200 L = 0.4998 M
Step 7: Calculate the pH using the concentration of the resulting acid. Since acetic acid is a weak acid, you need to consider its dissociation constant (Ka) to calculate the pH. Ka for acetic acid is 1.8 × 10^-5.
The equation for the dissociation of acetic acid is:
CH3COOH ⇌ H+ + CH3COO-
For every mole of acetic acid that dissociates, it will produce one mole of H+ and one mole of CH3COO-. Since the concentration of the resulting acid is the same as the concentration of CH3COO-, you can use this concentration to calculate the concentration of H+.
[H+] = √(Ka × concentration of resulting acid) = √(1.8 × 10^-5 × 0.4998) = 0.00316 M
Finally, calculate the pH using the concentration of H+:
pH = -log[H+] = -log(0.00316) = 2.50
Therefore, the pH of the solution is 2.50.