if i added (0.1N) 4.6 ml of NaOH to 10 ml of Ch3cooh calculate the ph
To calculate the pH of the solution after adding 4.6 mL of 0.1N NaOH to 10 mL of CH3COOH (acetic acid), you need to consider the reaction between the two compounds. Acetic acid is a weak acid, and NaOH is a strong base.
The reaction between CH3COOH and NaOH can be represented as follows:
CH3COOH + NaOH → CH3COONa + H2O
In this reaction, acetic acid reacts with sodium hydroxide to form sodium acetate (CH3COONa) and water. Sodium acetate is a salt that does not significantly affect the pH of the solution.
To determine the pH of the resulting solution, you need to assess the remaining concentration of acetic acid and the concentration of its conjugate base (acetate). You can calculate this using the concept of moles and molarity:
Step 1: Calculate the number of moles of acetic acid initially present.
- Convert the volume of acetic acid from mL to L: 10 mL ÷ 1000 = 0.01 L
- Calculate the number of moles of acetic acid: moles = volume (L) x molarity
moles = 0.01 L x 0.1 mol/L = 0.001 mol
Step 2: Calculate the number of moles of NaOH added.
- Convert the volume of NaOH from mL to L: 4.6 mL ÷ 1000 = 0.0046 L
- Calculate the number of moles of NaOH: moles = volume (L) x molarity
moles = 0.0046 L x 0.1 mol/L = 0.00046 mol
Step 3: Determine the dominant species after the reaction.
- The reaction between CH3COOH and NaOH is a 1:1 ratio. So, for the reaction to complete, all the moles of acetic acid will react with an equal number of moles of NaOH.
- Therefore, the amount of acetic acid remaining (in moles) will be: 0.001 mol - 0.00046 mol = 0.00054 mol
- The amount of sodium acetate formed will also be 0.00046 mol.
Step 4: Calculate the concentration of acetic acid and acetate after the reaction.
- Convert the combined volume of the solution from mL to L: (10 mL + 4.6 mL) ÷ 1000 = 0.0146 L
- Calculate the concentration of acetic acid: molarity = moles ÷ volume (L)
molarity_acetic acid = 0.00054 mol ÷ 0.0146 L = 0.0369 mol/L
- Calculate the concentration of acetate: molarity = moles ÷ volume (L)
molarity_acetate = 0.00046 mol ÷ 0.0146 L = 0.0315 mol/L
Step 5: Calculate the pKa or dissociation constant of acetic acid.
- The pKa of acetic acid is approximately 4.76.
Step 6: Use the Henderson-Hasselbalch equation to calculate the pH of the solution.
- pH = pKa + log [acetate]/[acetic acid]
pH = 4.76 + log (0.0315/0.0369)
pH = 4.76 + log (0.855)
pH ≈ 4.76 + (-0.068)
pH ≈ 4.692
Therefore, the pH of the solution after adding 4.6 mL of 0.1N NaOH to 10 mL of CH3COOH is approximately 4.692.