Chemistry – Acids, bases and salts - The characteristic properties of acids and bases | e-Consult

Test for Strength of a Base:

Reagents:

• Small amounts of the base to be tested.
• Universal indicator solution.
• Distilled water.

Procedure:

1. Add a small amount of the base to be tested to separate test tubes.
2. Add a few drops of universal indicator solution to each test tube.
3. Add distilled water to another set of test tubes.
4. Observe the colour change in the universal indicator solution in each test tube.

Observations:

• Strong Base: The universal indicator solution will turn a colour significantly different from yellow (e.g., blue, violet, green). The pH will be high (typically above pH 10).
• Weak Base: The universal indicator solution will change colour only slightly from yellow, remaining closer to yellow (e.g., a pale green or light blue). The pH will be relatively low (typically between pH 7 and 10).
• Water: The universal indicator solution will remain yellow, indicating a pH of approximately 7.

Reasoning:

Strong bases completely dissociate in water, producing a high concentration of hydroxide ions (OH^-). This results in a high pH and a significant change in the pH indicator's colour. Weak bases only partially dissociate in water, producing a lower concentration of hydroxide ions. This results in a lower pH and a smaller change in the pH indicator's colour.