Indicators

Q.

What are natural indicators? Give examples. What are universal indicators?

Q.

Is the distilled water acidic/basic/neutral? How would you verify it?

Q.

Give the reaction of Aluminium and Potassium hydroxide.

Q.

Question 4
Is distilled water acidic, basic or neutral? How would you verify it?

Q.

Indicator is a substance which shows different colours in acidic and basic solutions.

1. True

2. False

Q.

Explain the term acidity of a base?

Q. When turmeric juice is added to vinegar then the colour of the solution:

1. changes to brick red.
2. changes to blue.
3. changes to green.
4. does not changes.

Q.

Acetic acid will turn red litmus to

1. Pink

2. Blue

3. Dark blue

4. Red

Q.

Which of the following is not considered as an indicator?

1. Phenolphthalein

2. Methyl orange

3. Methyl chloride

4. Turmeric

Q.

Is vinegar acidic/basic/neutral? How would you verify it? [2 MARKS]

Q. What will happen if we mix a turmeric solution to soap solution and test it on both litmus papers??

Q. What are indicators? How are they classified?

Q. Lemons and vinegar are acidic in nature. They taste .

1. sour
2. bitter
3. salty

Q.

Identify the change in colour, when curd is tested with litmus paper.

1. Red litmus to green.

2. Blue litmus to red.

3. Red litmus to blue.

4. Blue litmus to green.

Q. What will be the effect of lime water, salt solution, vinegar, milk, sea water and curd on blue litmus paper?

Q.

Indicators are substances which show whether the substance tested is basic or acidic.

1. True

2. False

Q.

Why turmeric paper change it's colour when I pour a base?

Q.

State whether the following statements are true or false. Correct the false statements. [5 MARKS]
(a) All substances are either acidic or basic.
(b) A compound if acidic will turn all indicators red.
(c) Lime water turns red litmus blue.
(d) Common salt dissolved in water turns blue litmus red.
(e) Phenolphthalein is a natural indicator.

Q. What is bromocresol green?

Q.

What of the following indicators shows any change when distilled water is added to them?

1. Red Litmus

2. Blue litmus

3. No change in any indicator

4. Turmeric powder solution

Q.

What is an acid-base indicator? Name two naturally occurring indicators.

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

1. Onion
2. Clove
3. Red cabbage extract
4. Vanilla extract

Q.

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

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

Q.

State True or False. [3 MARKS]

a) Olfactory indicators respond to acid or base by change in smell.
b) When an aqueous solution of shampoo is mixed with the extract of red cabbage, the solution turns pink.
c) Methyl Orange is a natural Indicator.

Q.

Indicator litmus test on diluted hydrochloric acid, diluted sodium hydroxide, diluted nitric acid can you show the effect of litmus paper, effect on turmeric paper, effect on China rose

Q.

Identify X, Y, and Z in the given reaction sequence.

$\mathrm{Al}+\mathrm{NaOH}\to \mathrm{X}\stackrel{\mathrm{Y}\left(\mathrm{g}\right)}{\to }\mathrm{Z}$

1. $\mathrm{X}=\mathrm{Na}\left[\mathrm{Al}{\left(\mathrm{OH}\right)}_4\right];\mathrm{Y}={\mathrm{CO}}_2;\mathrm{Z}={\mathrm{Al}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$

2. $\mathrm{X}=\mathrm{Na}\left[\mathrm{Al}{\left(\mathrm{OH}\right)}_4\right];\mathrm{Y}={\mathrm{SO}}_2;\mathrm{Z}={\mathrm{Al}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$

3. $\mathrm{X}=\mathrm{Al}{\left(\mathrm{OH}\right)}_3;\mathrm{Y}={\mathrm{CO}}_2;\mathrm{Z}={\mathrm{Al}}_2{\mathrm{O}}_3$

4. $\mathrm{X}=\mathrm{Al}{\left(\mathrm{OH}\right)}_3;\mathrm{Y}={\mathrm{SO}}_2;\mathrm{Z}={\mathrm{Al}}_2{\mathrm{O}}_3$

Q. Can we use the same blue litmus paper that turned into red when poured a drop of acid, again to obtain blue litmus paper again.
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Q. Rima wrote a secret message in a paper using a solution X. Neha was able to read it as the letters turned green when rubbed with a solution Y. Identify X and Y.

1. X - Soap solution
   Y - Vinegar
2. X - Vinegar
   Y - Phenolphthalein
3. X - Lime water
   Y - Phenolphthalein
4. X - Soap solution
   Y - Red cabbage juice

Q.

A student dipped a pH paper first in distilled water and then aqueous NaCl solution. In both the cases, the colour of the pH value remained green. What does it indicate ?

Q. Phenolphthalein does not show any colour change in the presence of water.

1. True
2. False