Answer: To identify acids and alkalis using an indicator, you can follow the steps below:
Select an appropriate indicator: One commonly used indicator is litmus paper, which comes in red and blue forms. Red litmus paper turns blue in the presence of an alkali, while blue litmus paper turns red in the presence of an acid. Another widely used indicator is phenolphthalein, which is colorless in acidic solutions and turns pink in the presence of an alkali.
Prepare the test samples: Obtain a small amount of the substance you wish to test for acidity or alkalinity. Dissolve a small portion of the substance in water to create a test solution.
Perform the test with an acid: Dip the red litmus paper into the test solution. If the litmus paper turns blue, it indicates the presence of an alkali. However, if the red litmus paper remains red, it means the solution is either neutral or acidic. To confirm whether it is an acid, use the blue litmus paper. If the blue litmus paper turns red, it confirms the presence of an acid.
Perform the test with an alkali: If the red litmus paper did not turn blue when testing with an acid, dip the blue litmus paper into the test solution. If the blue litmus paper turns red, it indicates the presence of an acid. However, if the blue litmus paper remains blue, it means the solution is either neutral or alkaline. To confirm whether it is an alkali, use phenolphthalein indicator. If the solution turns pink, it confirms the presence of an alkali.
It's important to note that there are many other indicators available, such as bromothymol blue, methyl orange, and universal indicator, which provide a range of colors to indicate the pH of a solution. The choice of indicator may vary depending on the specific requirements of the experiment or analysis being conducted.
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