Universal Indicator

Q.

What is an indicator? Give example.

Q.

What is a Universal indicator?

Q.

What is the original colour of phenolphthalein?

Q. What is litmus solution?

Q.

How do indicators actually change color

Q.

What would be the colour of litmus in a solution of sodium carbonate ?

Q.

Why is potassium dichromate not a self indicator?

Q.

(a) What is a universal indicator? For what purpose is it used?

(b) How does a universal indicator work?

(c) 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?

Q.

Solution A gives pink color when a drop of phenolphthalein indicator is added to it. Solution B gives red color when a drop of methyl orange is added to it. What type of solutions are A and B and which of these will have a higher pH value?

Q.

Consider the following statements

1. Both acids and bases change the colour of all indicators.
2. If an indicator gives a colour change with an acid, it does not give a change with a base.
3. If an indicator changes colour with a base, it does not change colour with an acid.
4. The change of colour in an acid and a base depends on the type of indicator.

Which of these statements are correct?

1. All four

2. a and d

3. b, c, and d

4. only d

Q.

Distinguish between:

(a) a common acid-base indicator and a universal indicator,

(b) the acidity of bases and basicity of acids,

(c) acid and alkali (other than indicators).

Q. A universal indicator can detect what range of pH values?

1. 0 - 14
2. 4 - 10
3. 7 - 14
4. 0 - 7

Q.

Universal indicator imparts orange color to a solution. Predict the pH of a solution.

Q.

When you use a universal indicator, you see that solutions of different acids produce different colours. Indeed, solutions of the same acid with different concentrations will also give different colours, Why?

Q.

A blue litmus paper was first dipped in dil. Hcl and then in dil NaoH solution what can be observed?

Q.

What can a universal indicator indicate?
(i) Whether a solution is acidic.
(ii) Whether a solution is basic.
(iii) The pH of the solution.
(iv) Whether a base is strong or weak.
(v) Whether an acid is strong or weak.

1. (i), (ii)
2. (iii), (iv), (v)
3. (i), (ii), (iii)
4. (i), (ii), (iii), (iv), (v)

Q.

On adding a few drops of universal indicator to three colourless solutions taken separately in three test tubes labeled P, Q, R respectively, the colours developed in the solutions are marked in the following figures:

What is the correct decreasing order of pH values of the solutions.

1. R > P > Q

2. P > Q > R

3. R > Q > P

4. Q > P > R

Q.

Why HCl gas is unable to change the colour of a dry blue litmus paper ? What happens if the paper is moistened ?

Q. A solution X gives orange colour when a drop of universal indicator is added to it. In the other hand, another solution Y gives blueish green colour when a drop of universal indicator is added to it. What are the types of solution X and Y and what type of pH would they have?

Q.

An example of a natural indicator:

1. Methyl Orange

2. Litmus

3. Phenolphthalein

4. All of the Above.

Q.

Two solutions X and Y are tested with universal indicator. Solution X turns orange whereas solution Y turns red. Which of the solutions is a stronger acid?

Q. What are olfactory indicators and litmus paper

Q.

Bases turn methyl orange indicator

1. red

2. green

3. yellow

4. blue

Q.

The indicators litmus paper, phenolphthalein, and methyl orange are commonly used in

1. Hospitals.

2. Homes.

3. Laboratories.

4. Airports.

Q.

Which of the following salt is basic in nature?

1. Sodium chloride

2. Sodium acetate

3. Potassium nitrate

4. Aluminium chloride

Q.

Assertion: Phenolphthalein is an acid-base indicator.

Reason: In an acid-base titration, this indicator is used.

1. Both Assertion and Reason are false.

2. Assertion is false, but Reason is true.

3. Both Assertion and Reason are true. The reason is the correct explanation of Assertion.

4. Both Assertion and Reason are true. The reason is not the correct explanation of Assertion.

Q.

When concentrated nitric acid is added to a sample of cooking oil to detect the adulteration, it turns

1. Yellow in colour

2. Black in colour

3. Reddish-brown in colour

4. Yellowish-brown in colour

Q. The reaction in which there is an exchange of ions between the reactants is known as _______.

1. combination reaction
2. decomposition reaction
3. displacement reaction
4. double displacement reaction

Q.

Name the indicator which can give us an idea of how strong or weak an acid or base is.

Q.

A colorless solution has a pH close to 3. What will be the change in color if a few drops of phenolphthalein are added?