ICSE Class 9 Chemistry Additional Charts 01 Preparation of Gases

Chart 1: Preparations Of Gases - Hydrogen

Hydrogen

Nature

Neutral gas, which is colourless, odourless, tasteless and non-toxic.

Density

1000 ml. of gas at S.T.P. weighs 0.09 g. Hydrogen is the lightest gas known.

Solubility

100 vols. of water dissolves about 2 vols. at S.T.P. Hydrogen is slightly soluble in water.

Preparation - General Methods and Laboratory Preparation

General Methods From - Water

From cold water - reaction highly exothermic.

\[2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2\]

From boiling water or steam

\[\text{Mg} + \text{H}_2\text{O} \rightarrow \text{MgO} + \text{H}_2\]

\[\text{Zn} + \text{H}_2\text{O} \rightarrow \text{ZnO} + \text{H}_2\]

\[3\text{Fe} + 4\text{H}_2\text{O} \rightleftharpoons \text{Fe}_3\text{O}_4 + 4\text{H}_2\]

General Methods From - Acids

\[\text{2Na} + 2\text{HCl [dil.]} \rightarrow \text{MgCl}_2 + \text{H}_2\]

\[2\text{Al} + 3\text{H}_2\text{SO}_4 \text{ [dil.]} \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{H}_2\]

General Methods From - Alkalies

\[\text{Zn} + 2\text{KOH} \rightarrow \text{K-ZnO}_2 + \text{H}_2\]

\[\text{Pb} + 2\text{NaOH} \rightarrow \text{Na}_2\text{PbO}_2 + \text{H}_2\]

\[2\text{Al} + 2\text{NaOH} + 2\text{H}_2\text{O} \rightarrow 2\text{NaAlO}_2 + 3\text{H}_2\]

Laboratory Preparation - From Granulated Zinc and Dilute HCl

\[\text{Zn} + 2\text{HCl [dil.]} \rightarrow \text{ZnCl}_2 + \text{H}_2\]

Removal of impurities - Impurities obtained are remove by passage through - washer bottles containing AgNO3, Pb(NO3)2 and KOH solutions to remove - arsine, hydrogen sulphide and NO2, CO2, SO2 impurities respectively.

Collection of gas - Downward displacement of water.

Teacher's Note

Hydrogen gas is produced industrially and used in many everyday applications such as fuel cells for vehicles and ammonia synthesis for fertilizers. Understanding its preparation helps us appreciate modern energy solutions.

Preparation - Industrial Method - Bosch Process

Step I - Production of Water Gas

\[\text{C} + \text{H}_2\text{O} \xrightarrow{1000^\circ\text{C}} \text{CO} + \text{H}_2 - \triangle\]

[coke] [steam] [water gas]

Step II - Reduction of Steam to Hydrogen

\[\text{CO} + \text{H}_2 + \text{H}_2\text{O} \xrightarrow{450^\circ\text{C}} \text{CO}_2 + 2\text{H} + \triangle\]

[water gas] [steam] [Fe2O3, Cr2O3]

Step III - Recovery of Hydrogen From the Above Mixture

Removal of CO2 - By dissolving above mixture in water under pressure or in caustic potash soln.

Removal of CO - By dissolving in ammoniacal cuprous chloride.

Teacher's Note

The Bosch Process is a century-old industrial method still used today to produce hydrogen at scale. Its multi-step approach demonstrates how chemical engineering converts raw materials into useful products efficiently.

Reference Chart - Preparations Of Gases (Contd.)

Teacher's Note

These five gases represent some of the most important gases in chemistry and everyday life. From nitrogen in fertilizers to oxygen for respiration to carbon dioxide in carbonated drinks, understanding their properties helps us recognize their practical uses around us.

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