Evaluate the accurate acid concentration of a sulphuric acid solution which is formed as a by-product of the extraction of a metal from its original ore.

(Source Information sheet on the use of indicators in acid alkali solutions)

I also managed to obtain some information on the suitability of each indiactor to each reaction:

• Titration between a strong acid and a weak alkali→ methyl orange indicator
• Titration between weak acid and strong alkali→ Phenolphthalein indicator
• Titration between strong acid and strong alkali→ methyl orange is usually chosen
• Titration between weak acid and weak alkali→ no indicator is suitable pH meter; conductivity meter or temperature probe has to be used.

On the bases of the information collected above I set up the apparatus for my experiment.

Prediction:

I predict that the acid concentration will lie between the following values: 0.05 and 0.15 mol dm3.

Apparatus:

Method:

• With the aid of the measuring cylinder I will measure the exact volume of Sulphuric acid, which I will later place into the burette (     ). It is important that the Measuring Cylinder is clean, so that the acid does not react with other substances, which could have earlier been present in the cylinder. Any small additions or adjustements will be carried out with the use of the pipette.

• I will accurately weight out the exact mass of anhydrous sodium carbonate (    ), which will react with the sulphuric acid. It is important that the balance is set on 0 (g) before the solid is weighted.

• I will then stirr the acid that will be contained in a beaker, in this way more kinetic energy will be transferred to the acid particles, which increases the rate of reaction. I will then place the sulphuric acid solution into the Burette, filling it up to the top. A filter funnel will aid me into doing so, by making sure that no acid is spilled on the workstation. The Burette will be locked so that no acid drips from the bottom end, until the reaction has started.

• I will place the anhydrous sodium carbonate into a clean beaker, and place it under the burette. Everything is set up for the reaction to start takin place.

• The lock in the burette will be released, and the acid will transfer into the beaker containing the solid alkali. It is important to control the amounts of acid, which transfer each time, so that at the end of the reaction we know exactly how much acid was needed for the neutralisation to take place. When the colur of the solution has mutated, this indicates that the reaction has been completed.

• When the colour of the solution has changed we will introduce the methyl orange indicator into to solution, which will tell us the exact pH.

• We will record our results in a table, to then obtain a graphical representation, which will aid us into drawing a conclusion from a re given results.

Control variables:

• I will have to make sure that the Measuring cylinder is clean before the acid id placed in it, so that the acid does not react with any other substances before the start of the neutralisation reactions.

• I will have to make sure that the volume of acid which is transferred from the burette into the beaker containing the solid alkali, each time is constant, so that it is possible to measure the total volume of acid which has been transferred to the beaker.

• If any repeats are carried out I have to make sure that the solid catalyst is always in the same form: powdered form. If was to be in different forms, there would be varying surface areas. Which would lead to different rates of reactions.