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प्रश्न
Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are
विकल्प
red and blue
blue and red
pink and colourless
colourless and pink
उत्तर
colourless and pink
Explanation:
Phenolphthalein remains colourless in acidic solution and turns pink in basic solution.
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संबंधित प्रश्न
Tooth decay is caused by the presence of a base.
What is produced if an acid is added to a base?
When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.
- What are X, Y and Z?
- Write equations for the reactions which take place:
- When limestone reacts with dilute HCl.
- When gas X reacts with lime water to form white precipitate Y.
- When excess of gas X dissolves white precipitate Y to form a soluble compound Z.
The salt which will give an acidic solution on dissolving in water is:
(a) KCl
(b) NH4Cl
(c) Na2Co3
(d) CH3COONa
Sulphuric acid has the highest importance in the chemical industry. Why?
Give the reaction of acid with nitrates. State the conditions under which they react.
What are the uses of acids?
Fill in the crossword given in Figure 5.2 with the help of the clues provided.
Across
(2) The solution which does not change the colour of either red or blue litmus.
(4) Phenolphthalein gives pink colour in this type of solution.
(7) Colour of blue litmus in lemon juice.
Down
(1) It is used to test whether a substance is acidic or basic.
(3) It is a natural indicator and gives pink colour to the basic solution.
(5) Nature of ant’s sting.
(6) It is responsible for the increase in temperature during a neutralisation reaction.
Write the important uses of hydrochloric acid and sulphuric acids.
Match the following:
| 1. | The hardest substance in our body | a. | Aluminum phosphate |
| 2. | Citrus fruits | b. | Potash alum |
| 3. | Rice plant | c. | Insoluble in water |
| 4. | Double salts | d. | Acidic soil |
| 5. | Silver chloride | e. | Calcium phosphate |
| f. | Alkaline soil |
