Calculate the pH of a buffer solution containing 1.0 mol/dm3 CH3COONa.
I need a step by step solution and explanation. thank you
If it contains CH3COONa, that acts as a pseudo buffer but it isn't a real buffer. A real buffer would also contain acetic acid, CH3COOH. The pH of a 1 mol/dm^3 sodium acetate solution has a pH of.........
.........CH3COO^- + HOH ==> CH3COOH + OH^-
I..............1 M.................................0...................0
C............-x.....................................x....................x
E...........1-x.....................................x...................x
Kb for CH3COO^- = (Kw/Ka) for CH3COOH) = (x)(x)/(1-x)
Solve for x = (OH^-) and convert to pH. Post your work if you get stuck.
To calculate the pH of a buffer solution containing CH3COONa, you need to consider the dissociation of the acetic acid (CH3COOH) and its conjugate base, acetate ion (CH3COO-). Here's how you can proceed step by step:
Step 1: Write the chemical equation for the dissociation of acetic acid:
CH3COOH ⇌ CH3COO- + H+
Step 2: Determine the concentration of the acetic acid. In this case, it is given that the concentration of CH3COONa is 1.0 mol/dm3. Since CH3COONa is a salt of acetic acid, it dissociates completely, meaning that the concentration of CH3COO- is also 1.0 mol/dm3. So, the initial concentration of CH3COOH is also 1.0 mol/dm3.
Step 3: Use the Henderson-Hasselbalch equation to calculate the pH of the buffer solution:
pH = pKa + log ([A-]/[HA])
where pKa is the acid dissociation constant of acetic acid, [A-] is the concentration of the acetate ion, and [HA] is the concentration of acetic acid.
Step 4: Find the pKa value of acetic acid, which is 4.76.
Step 5: Substitute the values into the Henderson-Hasselbalch equation:
pH = 4.76 + log (1.0/1.0)
Step 6: Simplify the equation:
pH = 4.76 + log (1)
Step 7: Since the logarithm of 1 is equal to 0, the calculation becomes:
pH = 4.76 + 0
pH = 4.76
Therefore, the pH of the buffer solution containing 1.0 mol/dm3 CH3COONa is 4.76.