Experiments to Determine the Effect of Acids & Bases on Different Indicators and the pH of Common Cleaning Agents
The aim of the first set of experiments is to find out and record the colour changes that are observed after a certain indicator is mixed with acids and bases to form a colour reaction. Once the selected indicator has been mixed with a acid that is both weak and strong and a base/alkali that is both weak and strong we are to record the colour and choose another indicator. The purpose of this experiment is to find out what indicators are sensitive to what areas of the pH colour spectrum, while also looking how Universal Indicator covers most areas of the pH spectrum generally ...view middle of the document...
Then one drop of Phenolphthalein was placed on the tile so that it landed in the previous drop of Hydrochloric Acid. This colour reaction was noted and then recorded on a results sheet. The tile was then placed under a fair quantity of water to clean it and then was dried off with some paper towel. Following the same steps as before one drop of the chosen weak acid, Sulfuric Acid 1M ( H2SO4 ) was placed on the tile using an eyedropper. Then one drop of Phenolphthalein was placed on the drop of Sulfuric Acid and the colour was noted and recorded on a results sheet. The tile was then washed after every pH sample to ensure that there was no contamination from other chemicals. The Phenolphthalein indicator was then tested with the chosen strong base, Sodium Hydroxide 2M ( NaOH ) and the chosen weak base, Sodium Hydroxide 1M. The indicators, Phenol Red, Methyl Red, Methyl Orange, Beomothymol Blue, Universal Indicator and Congo Red were then tested following the acids and bases as above. The only variation to this is that for Universal Indicator and Congo Red the weak base was Potassium Hydroxide ( KOH ).
In the second experiment, a white tile was placed on the bench together with a rack of test tubes. Approximately 30mls of water was placed in each of the six test tubes and then some domestic cleaning products were added to them. A small amount of bleach went in the first test tube, detergent in the second, Jiff Rinse Aid in the third and Ajax was placed in the fourth test tube. Then a small amount of Cloudy Ammonia was poured into the fifth test tube and Nifty was poured in the sixth test tube. At this point all of the six test tubes were rotated at high speed to make sure the solutes, which were the cleaners, had blended with the water to make a solution. Now a little amount of the diluted bleach was poured onto the tile and a drop of Universal Indicator placed on the solution. The colour was observed and compared to the colour spectrum displayed on the Universal Indicator pH chart. We cleaned the tile and went through this process for the detergent, Jiff's Rinse Aid, Ajax, Cloudy Ammonia and Nifty. At this point two of the test tubes were thoroughly washed in the sink to avoid contamination and filled with approximately 30mls of water again. Now a small amount of Spray 'n Wipe was placed in one test tube and a small amount of nail polish remover was placed in the other test tube. Both of these cleaning agents were poured separately on the tile and tested for their pH and had it recorded. Now we cleaned the tile and emptied the test tubes down the sink with large amounts of water to dilute the strong acids and bases.
The table below shows the results for the first experiment:
Strong Acid Colour
Weak Acid Colour
Strong Base Colour
Weak Base Colour
Hydrochloric Acid 2M
Sulfuric Acid 1M
Sodium Hydroxide 2M
Sodium Hydroxide 1M