Titration Calculations (OCR GCSE Chemistry A (Gateway Science Suite)): Revision Notes

Titration calculations determine the concentration of an unknown acid or base in a solution. By using the volume of titrant (a solution of known concentration) required to neutralise a known volume of analyte (the solution being tested), you can calculate the unknown concentration.

Worked Example: Calculating the Concentration of an Acid In this example, we'll calculate the concentration of hydrochloric acid (HCl) using data from a titration with sodium hydroxide (NaOH).

Given:

• Volume of NaOH solution: 25.0 cm³
• Concentration of NaOH solution: 0.100 mol/dm³
• The volume of HCl solution: 20.00 cm³ Goal: Find the concentration of the hydrochloric acid solution.

Step 1: Calculate the Amount of Sodium Hydroxide in Moles First, convert the volume of the sodium hydroxide solution from cm³ to dm³:

Use the formula:

Substituting the values:

Amount of NaOH = $0.100×0.0250=0.00250 mol$

Step 2: Find the Amount of Hydrochloric Acid in Moles

Using the balanced chemical equation:

The mole ratio of NaOH to HCl is 1:1. Therefore, the amount of HCl that reacted is the same as the amount of NaOH:

Amount of HCl = $0.00250 mol$

Step 3: Calculate the Concentration of Hydrochloric Acid in mol/dm³

Convert the volume of the hydrochloric acid solution from cm³ to dm³:

Now, calculate the concentration using the formula:

Substituting the values:

Step 4: Calculate the Concentration of Hydrochloric Acid in g/dm³

To find the concentration in g/dm³, use the relative formula mass (Mᵣ) of HCl:

Now calculate the mass:

So, the concentration of hydrochloric acid in g/dm³ is: