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Control and Coordination
Question
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A solution turns red litmus paper blue. What does this indicate about the chemical nature of the solution?

Answer

The changing colour of litmus from red to blue is a characteristic of the substances called bases or alkalies. Metal hydroxide like potassium hydroxide change the colour of red litmus to blue litmus.

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Some More Questions From Control and Coordination Chapter

What are indicators? Name four acid-base indicators and mention their colour change.

What are antacids?

What are olfactory indicators?

You are given the following solutions:

Hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric acid (HNO3), acetic acid (CH3COOH), sodium hydroxide (NaOH), calcium hydroxide [(Ca(OH)2], potassium hydroxide (KOH), magnesium hydroxide [Mg(OH)2] and ammonium hydroxide (NH4OH). Give the colour change for each of these solutions with red litmus, blue litmus, phenolphthalein and methyl orange solutions.

Choose the olfactory indicators and give their characteristics: red cabbage extract, onion, vanilla extract, litmus, clove oil.

What do you understand by concentrated and dilute acids?

How do metals react with bases?

What is a neutralization reaction? Give some examples.

What are non-metallic oxides? Substantiate your answer.

Take 5 ml hydrochloric acid in a boiling tube or a conical flask. Add a few pieces of zinc granules to it.

(a) What do you observe on the surface of zinc granules?
(b) Name the gas evolved.
(c) What happens when the above gas is passed through soap solution?
(d) What happens when a burning candle is brought near the gas filled tube?