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Question

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Answer the following:
(a) Why is Plaster of Paris written as ${CaSO}_{4} . \frac{1}{2} H_{2} O ?$ How is it possible to have half a water molecule attached to CaSO₄?

(b) Why is Sodium Hydrogen Carbonate an essential ingredient in antacids?

(c) When electricity is passed through an aqueous solution of sodium chloride, three products are obtained. Why is the process called chlor-alkali?

Solution

(a) Plaster of Paris is written as

{CaSO}_{4} . \frac{1}{2} H_{2} O,

because in this compound, 2 water molecules are attached to one calcium sulphate molecule.

(b) Sodium hydrogen carbonate is a mild base. It neutralize acidic character but does not impart noticeable basic character.

(c) When sodium chloride is electrolysed, sodium is obtained at cathode which then reacts with water to give alkali and hydrogen. Thus alkali is the main product. On the other hand, chlorine is obtained at anode. So it is called chlor-alkali process.

Some More Questions From Control and Coordination Chapter

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?

Name four acids and bases. Write their formulae.

Name the various kind of oxides and mention their properties.

What are acids? How are they produced?

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