Making a standard solution Learning Objectives Aiming for

Making a standard solution

Learning Objectives • Aiming for 4: Explain how the mass of a solute and the volume of a solution is related to the concentration of the solution. • Aiming for 6: To calculate the mass of a chemical when any volume and concentration is given. • Aiming for 8: Explain the concentration in terms of particles.

Amount (mol) Conc (mol/dm 3) Vol (dm 3) Amount (g) Conc (g/dm 3) Vol (dm 3)

Making a standard solution What is a standard solution? A standard solution is a solution whose concentration is known accurately. Its concentration is usually given in mol dm– 3. When making up a standard solution it is important that the correct mass of substance is accurately measured. It is also important that all of this is successfully transferred to the volumetric flask used to make up the solution.

Making a standard solution 1. Using a petri dish, weigh out the calculated mass of sodium 2. 3. 4. 5. 6. chloride. Transfer it to a 250 cm 3 beaker and dissolve the solid in no more than 100 cm 3 of distilled water by stirring gently with a glass rod. When it has all dissolved, use a funnel to transfer the solution to a 250 cm 3 volumetric flask. Rinse out the beaker with about 20 cm 3 of distilled water and transfer the washings to the 250 cm 3 volumetric flask. Make up to the graduation mark with deionised water, adding the water drop- wise up to the mark. The bottom of the meniscus should be level with the mark. Insert the stopper and invert the flask several times so that the solution is thoroughly mixed.