Tetraammine Copper (II) Sulphate

Why is Plaster of Paris written as CaSO 4 . 1 2 H 2 O ? How is it possible to have half a water molecule attached to CaSO 4 ?

Plaster of Paris is prepared by heating gypsum at 373 K . The balanced equation is as follows: CaSO 4 . 2 H 2 O Gypsum → 373 k CaSO 4 . 1 2 H 2 O Plaster of paris + 3 2 H 2 O Water . It is not possible to have half a molecule of water. Therefore, actual formula must be 2 CaSO 4 . H 2 O . This means that, two molecules of calcium sulphate shares one molecule of water. Thus, the effective number of water molecules for one calcium sulphate is half. However, for the sake of simplicity, the plaster of Paris is shown as CaSO 4 . 1 2 H 2 O . That is, only half water molecule is shown as the water of crystallisation.

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A salt contains two types of ions, positive and negative. From where do these ions come?

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Important Questions on Acids, Bases and Salts

EASY

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The metal atom which is present in superphospahte is

EASY

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Complex salt is

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Write the chemical formulae for Washing-soda and Baking soda and give their uses.

HARD

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How is sodium hydroxide manufactured in industries? Name the process. In this process, a gas X is formed as a by-product. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reaction involved.

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Baking soda is a mixture of:

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A light greenish salt is soluble in water. On passing

H_{2} S

gas into the solution, a black precipitate is obtained which dissolves readily in

HCI

. The metal ion present is

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If excess of

{CO}_{2}

is passed through the suspension of a compound ‘X’ in water, a compound ‘Y’ is formed. Substances ‘X’ and ‘Y’ dissolve in

H_{2} {SO}_{4}

giving white compound ‘Z’ which is insoluble in water. Identify the compounds ‘X’, ‘Y’ and ‘Z’.

HARD

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How is washing soda prepared from sodium carbonate? Give its chemical equation. State the type of this salt. Name the type of hardness of water which can be removed by it?

EASY

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The chemical formula for plaster of Paris is:

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The