Indicators

Q.

What are natural indicators and synthetic indicators? Explain with examples.

Q. The colour of ______ litmus paper turns to _______ in the presence of an acid.​

1. red, pink​
2. blue, red​
3. red, blue
4. blue, pink

Q.

A few drops of phenolphthalein indicator were added to an unknown solution A. It acquired pink color. Now another unknown solution B was added to it dropwise and the solution ultimately became colorless. Predict the nature of solutions A and B.

Q.

Base added to a China rose solution shows which colour?

1. Acids turn blue litmus red

2. Acids turn red litmus blue

3. Acids taste sour

4. The chemical nature of acid is acidic

Q.

Mixtures of several indicators are known as the _________ indicator.

1. semi synthetic

2. Universal

3. Mixed

4. Synthetic

Q. What do you observe when

$\left(c\right)$. Blue litmus solution is added to water?

Q. Visual indicators change their on addition of an acid or a base.

1. state
2. colour
3. odour

Q. _________ turn blue litmus red whereas _________ turn red litmus blue.

1. Bases, acids
2. Acids, salts
3. Salts, Acids
4. Acids, bases

Q. What would be the colour change observed when a turmeric stained cloth is washed with soap?​

1. Yellow to Blue
2. Yellow to colourless
3. Yellow to pink
4. Yellow to red​

Q.

A large number of substances such as lemon, orange juice, baking soda and vinegar are used in daily life. Which of the following substance has a bitter taste?

1. Lemon

2. Vinegar

3. Orange juice

4. Baking soda

Q.

On adding phenolphthalein indicator to a colorless solution, no change is observed. What is the nature of this solution?

1. Basic

2. Either acidic or basic

3. Either acidic or neutral

4. Either basic or neutral

Q. Which of the following is an example of a visual indicator?

1. Clove

2. Onion

3. Extract of red cabbage

4. Vanilla extract

Q.

Litmus Is a natural dye obtained from

1. Fling

2. Virus

3. Lichens

4. Actinomycetes

Q. One of the major reasons for fading of the white colour of Taj Mahal is:​
​

1. Irrigation
2. Water harvesting
3. Acid rain
4. Heat Stroke​

Q.

Which colour will be acquired by an aqueous solution of ammonium hydroxide when a few drops of phenolphthalein indicator are added to it?

1. Yellow

2. Orange

3. Red

4. Pink

Q. What happens to the taste of the salt crystals if salt is mixed with sand?

1. Turns spicy
2. Turns sweet
3. Doesn't change
4. Turns sour

Q.

Turmeric, clove and rose petals are __ indicators.

Q.

(a) Name one indicator which turns red on adding an acid.

(b) Name one indicator which turns red on adding a base.

Q.

Methyl orange turns $\mathrm{HCl}$ from orange to

1. Pink

2. Yellow

3. Green

4. Blue

Q. Amisha has two solutions labelled 'A' and 'B'. On addition of phenolphthalein to each of them, solution A gives a pink colour, and solution B remains colourless. What can be determined about the nature of the solutions from the above observations?

1. A- Neutral, B- Acid
2. A- Neutral, B- Base
3. A- Base, B- Acid
4. A- Acid, B- Base

Q. Which of the following pairs of indicator and its colour in given medium are correct?

1. Litmus - Blue in acidic medium
2. Methyl orange - Red in acidic medium
3. Phenolphthalein - Pink in basic medium
4. Litmus - Red in basic medium

Q. Three test tubes contains different solutions and are labelled as A, B and C. The table below shows the observations when red and blue litmus papers were dipped in these test tubes.
Analyse the table given below and choose the correct options from the following.

$\begin{array}{cccc}& \text{Test tube A}& \text{Test tube B}& \text{Test tube C}\\ \text{Red Litmus}& \text{No change}& \text{No change}& \text{No change}\\ \text{Blue Litmus}& \text{Red}& \text{No change}& \text{Red}\end{array}$

1. The sample in test tube A is acidic
2. The sample in test tube A is neutral
3. The sample in test tube C is acidic
4. The sample in test tube B is neutral

Q. Universal indicator is :

1. the indicator that changes its colours at different iodide ion concentration
2. the indicator that shows different colours at different hydrogen ion concentrations
3. effective only at low hydrogen ion concentration
4. gives same colour at different pH

Q.

Which of the following can change the colour of red litmus to blue?

1. Sodium hydroxide

2. Sulphuric acid

3. Vinegar

4. Lemon juice

Q. What is an indicator? Give an example.

Q. All bases dissolve in water.

1. True
2. False