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प्रश्न
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?
उत्तर
(a) The students would have used universal indicator paper to measure the pH values of the substances. Universal indicator paper indicates different pH values of solutions with different colour changes. The strength of an acid or a base is known with the help of different colours.
(b) Lemon juice, with pH 2.5, is most acidic.
(c) Household ammonia, with pH 12.0, is most alkaline.
(d) Salt and sugar, with pH 7, are neutral.
(e) Vinegar, with pH 3, can be used to treat wasp stings. As a wasp sting is alkaline (pH > 7), an acid, such as vinegar, is applied to the skin, and it neutralises the base and soothes the pain.
(f) Baking soda, with pH 8.5, can be used to treat bee stings. As a bee sting is acidic (pH < 7), a base, such as baking soda, is applied to the skin, and it neutralises the acid and soothes the pain.
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संबंधित प्रश्न
Five solutions, A, B, C, D and E, when tested with universal indicator, showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is
- neutral?
- strongly alkaline?
- strongly acidic?
- weakly acidic?
- weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
What colour do the following indicators turn when added to a base or alkali (such as sodium hydroxide)?
litmus
Name an indicator which is red in acid solution but turns blue in basic solution.
Fill in the blank in the following sentences:
Acids have a ..........................taste and they turn..........................litmus to..........................
What is the effect of adding sodium hydroxide solution to these olfactory indicators?
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 does the pH of a solution signify? Three solution A, B and C have pH values of 6, 4 and 10 respectively. Which of the solutions is highly acidic?
A farmer has found that the pH of soil in his fields is 4.2. Name any two chemical materials which he can mix with the soil to adjust its pH.
A solution turns blue litmus red. Its pH is likely to be:
(a) 7
(b) 5
(c) 8
(d) 14
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 |
