Acid-base titration — KCSE Chemistry

In acid-base titration, we can determine the concentration of an unknown solution using the formula c₁V₁/n₁ = c₂V₂/n₂. Here, c represents concentration, V represents volume, and n represents the number of moles of the acid or base.

To apply this formula, follow these steps:

1. Identify the known and unknown concentrations (c₁, c₂).
2. Measure the volumes used in the titration (V₁, V₂).
3. Determine the number of moles from the balanced chemical equation (n₁, n₂).

For example, if you titrated 25 mL of hydrochloric acid (HCl) with 0.1 M sodium hydroxide (NaOH) and it took 30 mL of NaOH to reach the endpoint, you can calculate the concentration of HCl as follows:

• Given: c₂ = 0.1 M, V₂ = 30 mL, V₁ = 25 mL, n₂ = 1 (for NaOH), n₁ = 1 (for HCl).

• Substitute into the formula:

  c₁ = (c₂ * V₂ * n₁) / (V₁ * n₂) = (0.1 * 30 * 1) / (25 * 1) = 0.12 M.

Thus, the concentration of HCl is 0.12 M.

In acid-base titration, we determine the concentration of an acid or base by neutralizing it with a solution of known concentration. To calculate the number of moles, mass, or volume of a substance from titration results, follow these steps:

1. Identify the balanced chemical equation for the reaction.

2. Calculate the number of moles of the titrant used using the formula:

   [ \text{Moles} = \text{Concentration (mol/dm}^3) \times \text{Volume (dm}^3) ]

3. Use the mole ratio from the balanced equation to find moles of the other reactant.

4. Convert moles to mass using the formula:

   [ \text{Mass} = \text{Moles} \times \text{Molar Mass (g/mol)} ]

5. If required, calculate the volume of gas produced using the ideal gas law if the reaction involves gases.

For example, if 0.025 dm³ of 0.1 mol/dm³ NaOH is used to titrate HCl:

• Moles of NaOH = 0.1 mol/dm³ × 0.025 dm³ = 0.0025 moles.
• From the equation HCl + NaOH → NaCl + H₂O, the mole ratio is 1:1, so moles of HCl = 0.0025 moles.

Acid-base titration is a quantitative analytical technique used to determine the concentration of an acid or a base in a solution. It involves the gradual addition of one solution to another until the reaction reaches the equivalence point, where the amount of acid equals the amount of base. The key components of a titration setup include:

• Burette: Holds the titrant (the solution of known concentration).
• Pipette: Measures a specific volume of the analyte (the solution of unknown concentration).
• Indicator: A substance that changes color at the endpoint of the titration.

The process typically follows these steps:

1. Fill the burette with the titrant and record the initial volume.
2. Use the pipette to measure a specific volume of the analyte into a conical flask.
3. Add a few drops of the indicator to the analyte.
4. Gradually add the titrant from the burette to the analyte while swirling the flask until the endpoint is reached (color change).
5. Record the final volume in the burette and calculate the volume of titrant used.

This data can be used to calculate the concentration of the unknown solution using the formula: [ C_1V_1 = C_2V_2 ] (where C is concentration and V is volume).