Subjective Type

(a) What is a universal indicator? For what purpose is it used? (b) How does a universal indicator work? (c) Water is a neutral substance. What colour will you get when you add a few drops of universal indicator to a test-tube containing water?

Solution

(a) Universal indicator is a mixture of many different indicators which gives different colours at different pH values of the entire pH scale. It is used to obtain an idea of how acidic or basic a substance is.

(b) When an acid or base solution is added to the universal indicator, it produces a new colour which is used to find the pH value of the acid or the base solution by matching the colour with the colours on pH colour chart.

(c) When a drop of a universal indicator is added to the test tube containing water, it shows the green colour. This shows that the distilled water has pH = 7.

SIMILAR QUESTIONS

Acids, Bases and Salts

Write true or false for the following statement: The universal indicator shows the same color at different concentrations of hydrogen ions in a solution.

Acids, Bases and Salts

What is the name of the indicator which can be used for testing the pH of a solution?

Acids, Bases and Salts

What colour will universal indicator show if you add it to the following substances? (a) potassium hydroxide, pH = 12. (b) soda water, pH = 5. (c) sulphuric acid, pH = 2.

Acids, Bases and Salts

A beaker of concentrated hydrochloric acid has a $$pH$$ of $$1$$. What color will the full range universal indicator turn if it is added to this beaker? Is it a strong or a weak acid?

Acids, Bases and Salts

(a) What would you expect the pH of pure water to be? (b) What colour would the universal indicator show in an aqueous solution of sugar? Why? (c) A sample of rain water turned universal indicator paper yellow. What would you expect its pH to be? Is it a strong or a weak acid?

Acids, Bases and Salts

(a) What effect does the concentration of $$H^+$$ (aq) ions have on the nature of a solution? (b) What effect does the concentration of $$ OH^−$$ ions have on the nature of a solution? (c) Someone put some universal indicator paper into vinegar. The pH is 3. What does this tell you about the vinegar? (d) Someone put some universal indicator paper onto wet soap. The pH is 8. What does this tell you about the soap? (e) State whether a solution is acidic, alkaline or neutral if its pH is: (i) 9 (ii) 4 (iii) 7 (iv) 1 (v) 10 (vi) 3

Acids, Bases and Salts

Here are some results of solutions tested with universal indicator paper: Sulphuric acid: Red Metal polish: Dark blue Washing-up liquid: Yellow Milk of magnesia: Light blue Oven cleaner: Purple Car battery acid: Pink Arrange the solutions in order of their increasing pH values (starting with the one with the lowest pH).

Acids, Bases and Salts

Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red. (a) What will be the action of solution A on litmus? (b) What will be the action of solution B on litmus? (c) Name any two substances which can give solutions like A. (d) Name any two substances which can give solutions like B. (e) What sort of reaction takes place when solution A reacts with solution B?

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