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प्रश्न
What is an indicator? Name three common indicators.
What is an indicator?
उत्तर १
Indicators are substances that show a distinct change (colour or odour) simultaneous to a change in concentration of ions such as H+ and OH- ions.
Examples: Methyl orange, phenolphthalein and litmus solution.
उत्तर २
An indicator or acid-base indicator is a chemical substance which indicates the acidic or basic nature of a solution by suitable colour change.
संबंधित प्रश्न
You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
- Both acids and bases change colour of all indicators.
- If an indicator gives a colour change with an acid, it does not give a change with a base.
- If an indicator changes colour with a base, it does not change colour with an acid.
- Change of colour in an acid and a base depends on the type of the indicator.
Which of these statements are correct?
Name the scientist who developed the pH scale.
Two solutions A and B have pH values of 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink?
Fill in the following blank with suitable words:
Neutral substances have a pH of ................
Name two common antacids.
What effect does the concentration of OH− ions have on the nature of a solution?
A solution turns blue litmus red. Its pH is likely to be:
(a) 7
(b) 5
(c) 8
(d) 14
The daffodil plants grow best in a soil having a pH range of 6.0 to 6.5. If the soil in a garden has a pH of 4.5, which substance needs to be added to the soil in order to grow daffodils?
(a) salt
(b) lime
(c) sand
(d) compost
The pH values of five solutions A, B, C, D and E are given below:
| A | 1 |
| B | 5 |
| C | 7 |
| D | 11 |
| E | 13 |
Which solution isneutral neutral.
The pH values of five solutions A, B, C, D and E are given below:
| A | 1 |
| B | 5 |
| C | 7 |
| D | 11 |
| E | 13 |
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 batter acid | : Pink |
Arrange the solutions in order of their increasing pH value (starting with the one with the lowest pH).
In basic solution turmeric indicator paper changes from yellow to _______.
In acidic solution, the colour of the hibiscus indicator paper will change to _____.
Methyl orange gives ______ colour in an acidic solution.
Write a note on:
Litmus
Take a small beetroot vegetable and cut it into pieces. Boil them in hot water and filter the extract. Take two test tubes. Take sodium hydroxide solution in one test tube and vinegar or lemon juice in another test tube. Add beetroot extract slowly. Observe the colour change. What do you infer?
A milkman adds a very small amount of baking soda to fresh milk. Why does this milk take a long time to set as curd?
Prepare red cabbage juice by boiling a piece of red cabbage in water. Use it as an indicator and test the acidic and basic solutions with it. Present your observations in the form of a table.
