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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?
Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and the third is a sugar solution. How will you identify them? You have only turmeric indicator.
- 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?
Fill in the blank in the following sentences:
Acids have a ..........................taste and they turn..........................litmus to..........................
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
How does a universal indicator work?
The pH of a cold drink is 5. What will be its action on blue and red litmus solutions?
The pH values of three acids A, B and C having equal molar concentrations are 5.0, 2.8 and 3.5 respectively. Arrange these acids in order of the increasing acid strengths.
When a solution becomes more acidic, does the pH get higher or lower?
A solution turns phenolphthalein indicator pink. The most likely pH of this solution will be:
(a) 6
(b) 4
(c) 9
(d) 7
The colour of methyl orange indicator in a solution is yellow. The pH of this solution is likely to be:
(a) 7
(b) less than 7
(c) 0
(d) more than 7
Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red.
What sort of reaction takes place when solution A reacts with solution B?
A student prepares solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Acids and bases can be identified in the laboratory by ______.
Lemon juice will turn ______.
What is the colour of phenolphthalein in the basic solution?
Give names of any two natural indicators.
How will you prepare a china rose indicator?
Using the knowledge of acids and bases, write a secret message with the help of baking soda and beet root. Explain how it works.
(Hint: Prepare baking soda solution in water. Use this solution to write the message on a sheet of white paper with a cotton bud. Rub a slice of fresh beetroot over the message.)
