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प्रश्न
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
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उत्तर
- We know that basic and neutral solutions do not change the colour of blue litmus paper. Since blue litmus remains blue after dipping in the solution, the solution is either basic or neutral in nature.
- Put a drop of this solution on a red litmus paper. If it turns blue, the above solution is basic in nature. If no colour change occurs, it is neutral.
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संबंधित प्रश्न
The property which is common between vinegar and curd is that they:
(a) have sweet taste
(b) have bitter taste
(c) are tasteless
(d) have sour taste
What is the pH of a neutral solution?
What is the name of the indicator which can be used for testing the pH of a solution?
A sample of rain water turned universal indicator paper yellow. What would you expect it pH to be? Is it a strong or a weak acid?
Separate the following into substances having pH values above and below 7. How do these influence litmus paper?
(i) Lemon juice
(ii) Solution of washing soda
(iii) Toothpaste
(iv) Vinegar
(v) Stomach juices
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).
Explain why the pH in a person's mouth becomes lower after each meal.
A group of students measured the pH of some substances they found in their homes. Their results are given in the following table:
| Substance | pH | Substance | pH |
| Apples | 3.0 | Salt | 7.0 |
| Baking soda | 8.5 | Sugar | 7.0 |
| Black coffee | 5.0 | Toothpaste | 9.0 |
| Household ammonia | 12.0 | Vinegar | 3.0 |
| Lemon juice | 2.5 | Washing soda | 11.5 |
| Milk | 6.5 |
(a) What would the students have used to measure the pH?
(b) Which solution is the most acidic?
(c) Which solution is the most alkaline?
(d) Which solutions are neutral?
(e) Which solution can be used to treat wasp stings?
(f) Which solutions can be used to treat bee stings?
State whether the following statement is true or false. Correct the false statement.
Phenolphthalein is a natural indicator.
Add a few drops of hibiscus indicator to the soap solution. What do you observe?
