Preparation of Hydrogen - Laboratory and Industrial Methods

Zinc reacts with dilute hydrochloric acid to produce zinc chloride and hydrogen gas. This is a chemical reaction where zinc replaces hydrogen in the acid.

Granulated zinc is a form of zinc used in the laboratory. It is small pieces of zinc, increasing the surface area, making the reaction faster.

The gas produced from the reaction of zinc and dilute acid needs to be cleansed of impurities.

Impurities like arsine, phosphine, hydrogen sulphide, and sulfur dioxide are removed from the hydrogen gas.

The impure gas is passed through various solutions to absorb specific impurities. Silver nitrate solution absorbs arsine and phosphine, lead nitrate solution absorbs hydrogen sulphide, and potassium hydroxide solution absorbs nitrogen dioxide, carbon dioxide, and sulfur dioxide.

Anhydrous calcium chloride is used to absorb any remaining moisture from the hydrogen gas.

Hydrogen gas is collected by downward displacement of water. This method relies on hydrogen being less dense than water and collected above it.

The apparatus used to produce hydrogen gas must be airtight to prevent leaks and explosion. The thistle funnel should be below the acid level to prevent gas escaping through the funnel.

Removal of carbon dioxide from a mixture by dissolving it in water under pressure or a potassium hydroxide solution.

Removal of carbon monoxide from a mixture by dissolving it in an ammoniacal cuprous chloride solution.

The process of separating hydrogen from water by passing an electric current through it.

Generating hydrogen as a by-product during the electrolysis of brine (saltwater).

Methane (natural gas) reacts with steam at high temperatures to produce hydrogen and carbon monoxide.

The process of converting a vegetable oil into a semi-solid fat by adding hydrogen in the presence of a catalyst.

Hydrogenation of coal involves treating powdered coal with hydrogen gas under high pressure and temperature in the presence of a catalyst.

The ability of certain metals like platinum, nickel, gold, and palladium to absorb significant amounts of hydrogen on their surface.

The preferred acid to use for the reaction is dilute hydrochloric acid or dilute sulfuric acid. Nitric acid is not used because it is a strong oxidizing agent and oxidizes the hydrogen formed to water.

To increase the rate of the reaction, trace amounts of copper [II] sulfate are often added. This increases the reaction rate.

The process of collecting hydrogen involves displacing water downwards. This is because hydrogen is practically insoluble in water.

Although hydrogen is lighter than air, it is not collected by downward displacement of air because it forms an explosive mixture with air. The best method to collect pure dry hydrogen is over mercury or in a previously evacuated flask.

The Bosch process involves three distinct steps: 1. Production of Water Gas: Coke reacts with steam to produce water gas. 2. Reduction of Steam to Hydrogen: Water gas reacts with excess steam to produce more hydrogen. 3. Separation of CO2 & CO: Carbon dioxide and unreacted carbon monoxide are separated from the mixture.

The production of water gas involves an endothermic reaction where coke reacts with steam, generating carbon monoxide and hydrogen.

The reduction of steam to hydrogen is an exothermic reaction where water gas reacts with excess steam, producing more hydrogen and releasing heat.

In the Bosch process, carbon dioxide and unreacted carbon monoxide are separated from the mixture using appropriate methods, leaving behind hydrogen.