Chemistry NCERT Exemplar Solutions Class 11th Chapter Nine

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Option (i) and (ii)

The combination of CO and H₂ is known as water gas. This mixture of CO and H₂ is also known as synthesis gas or 'syngas' since it is used to make methanol and other hydrocarbons.

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Option (iii) and (iv)

H⁺ does not exist freely and is always associated with other atoms or molecules. It has an extremely high ionisation enthalpy and does not have metallic properties under normal conditions, unlike alkali metals.

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Option (i)

Group 6

From group 6, only chromium forms CrH.

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Option (i)

Groups 7,8, 9

Explanation: The metals belonging to group 7, 8 and 9 do not have tendency to form hydrides.

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Option (iii)

Na₆P₆O₁₈

Sodium hexametaphosphate (Na₆P₆O₁₈), commercially called 'calgon', is used to remove hardness from water.

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Option (i)

Ca²⁺

Water becomes 'hard' when it contains calcium and magnesium salts in the form of hydrogen carbonate, chloride, and sulphate.

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Option (iv)

CO (g)+2H₂ (g) → CH₃OH (l)

The reaction shown in equation (iv) shows the synthesis of methanol from water gas.

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Option (ii)

Sulphuric acid

2HSO₄^- (aq) → HO₃SOOSO₃H (aq) → 2HSO₄^- (aq)+2H⁺ (aq) + H₂O₂ (aq)

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Option (iv)

Sodium sulphate and hydrogen peroxide.

Na₂O₂+dil H₂SO₄ → Na₂SO₄ → Na₂SO₄+H₂O₂

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Option (iii)

CO (g)+H₂O (g) → CO₂ (g)+H₂ (g)

The production of dihydrogen can be increased by reacting carbon monoxide of syngas mixtures with steam in the presence of iron chromate as catalyst.