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Questions
What is an indicator? Name three common indicators.
What is an indicator?
Solution 1
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.
Solution 2
An indicator or acid-base indicator is a chemical substance which indicates the acidic or basic nature of a solution by suitable colour change.
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Is the distilled water acidic/basic/neutral? How would you verify it?
Fill in the blank in the following sentences:
Onion and vanilla extract are..........................indicators.
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Lemon juice, Vinegar, Banking soda solution
Give reason for your choice.
Name the indicator which can give us an idea of how strong or weak an acid or base is.
What is the name of the indicator which can be used for testing the pH of a solution?
How does a universal indicator work?
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?
The pH values of six solutions A to F are given below:
A = 0, B = 11, C = 6, D = 3, E = 13, F = 8
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What do you think will be the pH of an antacid solution: less than 7 or more than 7?
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 is weakly alkaline.
Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red
What will be action of solution B on litmus?
Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red.
Name any two substances which can give solutions like A.
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?
How will you prepare natural indicator from turmeric powder?
Acids and bases can be identified in the laboratory by ______.
Neutral substances do not bring about any change in colour of indicators.
Name any two synthetic acid-base indicators.
Take some lemon juice in a tumbler and add baking soda slowly. What do you see? What do you infer from this?
