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प्रश्न
What is an indicator? Name three common indicators.
What is an indicator?
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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
Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
Which of the following types of medicine is used for treating indigestion caused by over-eating?
(a) antibiotic
(b) analgesic
(c) antacid
(d) antiseptic
What colour will universal indicator show if you add it to the following substances?
(a) potassium hydroxide, pH = 12
(b) soda water, pH = 5
(c) sulphuric acid, pH = 2
A beaker of concentrated hydrochloric acid has a pH of 1. What colour will full range universal indicator turn if it is added to this beaker? Is it a strong or a weak acid?
Two drinks P and Q gave acidic and alkaline reactions, respectively. One has a pH value of 9 and the other has a pH value of 3. Which drink has the pH value of 9?
Two solutions X and Y have pH = 4 and pH = 8, respectively. Which solution will give alkaline reaction and which one acidic?
What effect does the concentration of OH− ions have on the nature of a solution?
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?
In basic solution turmeric indicator paper changes from yellow to _______.
Few drops of aqueous solution of ammonium chloride are put on a universal indicator paper. The paper turns pink.
Choose the correct option.
