Determine the pH at the equivalence point when 25.00 mL of 0.1056 M CH3COOH is titrated with 0.1056 M NaOH.
First you must calculate the M of the salt, NaAc (sodium acetatate) at the equivalence point. That will be millimols/mL. mmols NaAc = 25 x 0.1056 = approx 2.6 but you should do it more accurately. Since the M NaOH is the same you know it will take 25 mL of the NaOH; therefore, M NaAc = about 2.6/50 = approx 0.05.
The pH at the equivalence point is determined by the hydrolysis of the NaAc.
......Ac^- + HOH --> HAc + OH^-
I....0.05............0......0
C.....-x.............x......x
E....0.05-x..........x......x
Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(0.05-x).
Solve for x = (OH^-) and convert t pH.
To determine the pH at the equivalence point, we need to understand the nature of the reaction between acetic acid (CH3COOH) and sodium hydroxide (NaOH). The reaction can be represented as follows:
CH3COOH + NaOH -> CH3COONa + H2O
Here, acetic acid reacts with sodium hydroxide to form sodium acetate (CH3COONa) and water. At the equivalence point, the number of moles of acid will be equal to the number of moles of base added.
In this case, we have 25.00 mL of 0.1056 M acetic acid being titrated with 0.1056 M sodium hydroxide. Since the concentrations of acetic acid and sodium hydroxide are the same, we can assume that we will reach the equivalence point when 25.00 mL of sodium hydroxide is added.
To calculate the number of moles of acetic acid present in 25.00 mL, we can use the formula:
moles = concentration x volume
moles of acetic acid = 0.1056 M x 0.02500 L = 0.00264 moles
At the equivalence point, all of the acetic acid will react with the sodium hydroxide to form sodium acetate. This means that the concentration of acetic acid will be zero and the concentration of sodium acetate will be equal to the original concentration of acetic acid.
To calculate the concentration of sodium acetate at the equivalence point, we can use the formula:
concentration = moles / volume
concentration of sodium acetate = 0.00264 moles / 0.02500 L = 0.1056 M
Now, we can calculate the pH at the equivalence point. Sodium acetate is a salt of a weak acid (acetic acid) and a strong base (sodium hydroxide). When a weak acid reacts with a strong base, the resulting salt will hydrolyze in water, producing hydroxide ions (OH-) and decreasing the pH.
To calculate the pH, we need to determine the concentration of hydroxide ions produced by the hydrolysis of sodium acetate. Since sodium acetate is fully dissociated in water, the concentration of hydroxide ions will be equal to the original concentration of sodium acetate (0.1056 M).
The pH can be calculated using the formula:
pOH = -log10[OH-]
pOH = -log10(0.1056)
pOH = 0.9786
To convert pOH to pH, we can use the formula:
pH = 14 - pOH
pH = 14 - 0.9786
pH = 13.0214
Therefore, the pH at the equivalence point when 25.00 mL of 0.1056 M acetic acid is titrated with 0.1056 M sodium hydroxide is approximately 13.0214.