Natural Indicators

Q.

What is an universal indicator?

Q. Cut surface of an apple turns brown.

Q.

Question 8

A solution changes the colour of turmeric indicator from yellow to red. The solution is
(a) basic
(b) acidic
(c) neutral
(d) either neutral or acidic

Q. What colour does china rose indicator gives witha acid and bases?

Q. Change of apple's colour into brown is a chemical change. Explain why?

Q. Turmeric stain on a shirt changes to ______ colour, when it is washed with soap.

1. red
2. white
3. blue
4. yellow

Q.

Question 10

On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution?
(a) Basic
(b) Either acidic or basic
(c) Either acidic or neutral
(d) Either basic or neutral

Q. Which of the following substances change red litmus paper to blue?

1. Milk of magnesia
2. Tomato
3. Soap
4. Limewater

Q.

Which of the following solution will change the color of blue hibiscus paper from blue to red?

1. Hydrochloric acid

2. Potassium hydroxide

3. Limewater

4. Caustic soda

Q.

Question 3

Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would be observed
(a) Yellow in both acid and base.
(b) Yellow in acid and red in base.
(c) Pink in acid and yellow in base.
(d) Red in acid and blue in base.

Q. Red litmus paper turns ______, when it is placed in limewater.

1. green
2. blue
3. black
4. yellow

Q. Choose the correct statement from the following options.

1. Citric acid will turn red litmus to blue.
2. Acetic acid will turn red litmus to blue.
3. Sodium hydroxide will turn red litmus to blue.
4. Potassium hydroxide will turn blue litmus to red.

Q.

Blue litmus solution is added to two test tubes A and B containing dilute$\mathrm{HCl}$ and $\mathrm{NaOH}$ solution respectively. In which test tube a colour change will be observed? State the colour change and give its reason.

Q.

How do we test whether a substance is an acid or base? Give example of some substances that can be used for testing acids and bases. [3 MARKS]

Q.

What is a litmus solution? How is it obtained?

Q.

A solution turns red litmus blue and turns phenolphthalein solution pink. The solution is a acid or a base?

Q.

The red cabbage will give pink colour in

1. Lime water
2. Vinegar
3. Lemon
4. Soap

Q. How can we distinguish between acids and bases using the litmus paper indicator?

Q.

Is hibiscus an indicator ?

Q. Which of the following substances turn blue litmus red?

1. Carbonated drinks
2. Soap solution
3. Pickles
4. Tea

Q.

Question 20

Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results.

Q.

Which of the following is a property of an acid?

1. sour taste

2. sweet taste

3. bitter taste

4. salty taste

Q.

A solution changes the colour of turmeric indicator from yellow to red. The solution is:

1. acidic in nature.

2. basic in nature.

3. neutral in nature.

4. Either neutral or acidic in nature.

Q. State three differences between acids and bases.

Q. Olfactory indicators change their colour when added to an acidic or a basic solution.

1. True
2. False

Q.

Which of the following is true about bases?

1. It turns blue litmus red
2. It turns red cabbage extract green
3. It has no effect on red cabbage extract
4. It has no effect on red litmus

Q. Bases change blue litmus to red.

Q. Which of the following is true for the distilled water?

1. It turns blue litmus to red.
2. It turns red litmus to blue.
3. It turns turmeric solution red.
4. It shows no colour change with any indicator.

Q.

Why do visual indicators show a change in colour when introduced to an acidic and basic medium?

Q.

Phenolphthalein is prepared by dissolving phenolphthalein dye in alcohol.

1. True
2. False