Are you a teacher looking for experiment ideas? The Chemistry Olympiad is at your service! Our volunteers have broken down an experiment from the final round into three bits suitable for a lesson which will be published here. Part 1: Qualitative analysis of effervescent tablets.
In the laboratory at the Chemistry Olympiad final. (Source: Luca Ferrari, ETH Zurich)
Duration: ca. 30 minutes Difficulty: Medium
A PDF download of this task sheet as well as the answers and instructions for preparing the experiment can be found here.
Procedure for the determination of divalent cation composition of the two tablets
Dissolve the effervescent tablet in deionized water in a 100 ml beaker. You may use a mortar and pestle to crush the tablets. Make sure to rinse the mortar and pestle well with deionized water after each tablet. Don't fill the beaker up right away but try to add a smaller amount of deionized water initially and swirl to dissolve the tablet. You may add dil. Hydrochloric acid until the tablet is completely dissolved.
Fill the beaker at most up to the 100 ml mark with deionized water.
You have received two different effervescent tablets, which are often used to re-establish electrolyte balance after exercise or illness. Using the following materials and chemicals, determine the cation composition of the tablets:
(Ion Sheet for Qualitative Inorganic Analysis)
Ammonia solution
Deionized water
Diluted Hydrochloric acid
pH paper
Plastic or glass pipettes
Potassium oxalate solution
Small glass vials
Sodium Carbonate Solution
Sodium hydrogen Phosphate Solution
Sodium hydroxide solution
Theoretical question
What is the divalent cation composition of your two different effervescent tablets? Write down the reaction equations that helped you identify them.
Would you like to discover all three parts of the experiment now - and more? You will find what you are looking for in the Chemistry Olympiad teaching material archive.
