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.
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.
(a) Dark Purple colour at pH = 12.
(b) Orange Yellow colour at pH = 5.
(c) Red colour at pH = 2.
Write true or false for the following statement: The universal indicator shows the same color at different concentrations of hydrogen ions in a solution.
What is the name of the indicator which can be used for testing the pH of a solution?
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?
(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?
(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?
(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
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).
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?