Preparation of Hydrogen - Laboratory and Industrial Methods

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Questions and Answers

What is the primary reason nitric acid is not used as the acid in the reaction with zinc?

It produces gaseous impurities during the reaction.

It has a strong oxidizing effect that oxidizes hydrogen to water. (correct)

It is highly reactive with water, causing immediate dilution.

It requires a very high temperature to react with zinc.

Which acid is preferred for the reaction involving zinc that produces hydrogen?

Concentrated sulfuric acid

Nitric acid

Phosphoric acid

Dilute hydrochloric acid (correct)

How is hydrogen typically collected during experiments?

By downward displacement of air.

By upward displacement of gas.

By downward displacement of water. (correct)

By direct capture in a gas syringe.

What is the role of granulated zinc when used with dilute acids?

It produces gaseous impurities that need to be purified. Signup and view all the answers

In the Bosch process, what is the purpose of adding excess steam in STEP II?

To increase the yield of hydrogen. Signup and view all the answers

Which drying agent is used to remove moisture from the collected hydrogen?

Fused calcium chloride Signup and view all the answers

What is produced in STEP I of the Bosch process?

Water gas from coke and steam Signup and view all the answers

What is the function of iron(III) oxide in STEP II of the Bosch process?

It serves as a catalyst for the reduction of carbon monoxide. Signup and view all the answers

What is the main chemical reaction involved in hydrogenation of vegetable oils?

Addition of hydrogen to oils Signup and view all the answers

Which method is used to produce hydrogen from natural gas?

Reaction of methane with steam Signup and view all the answers

What is the approximate temperature range of the oxy-hydrogen flame used in welding and cutting?

2800°C Signup and view all the answers

In the hydrogenation process, which metals are useful as catalysts due to their ability to occlude hydrogen?

Platinum and Nickel Signup and view all the answers

What role does hydrogen play in the metallurgy process?

Reducing agent Signup and view all the answers

What is produced from hydrogenation of coal?

A product similar to petroleum Signup and view all the answers

Which solution is used to remove carbon monoxide in industrial processes?

Ammoniacal cuprous chloride solution Signup and view all the answers

What happens to water during the electrolysis process?

It is converted to hydrogen and oxygen Signup and view all the answers

What is the balanced chemical equation for the reaction between zinc and dilute hydrochloric acid?

Zn + 2HCl → ZnCl2 + H2 Signup and view all the answers

Which of the following is a precaution to take during the preparation of hydrogen gas?

Ensure no leakage of gas occurs. Signup and view all the answers

What is the purpose of using AgNO3 solution in the first washer bottle during the purification of hydrogen gas?

To absorb impurities like arsine and phosphine. Signup and view all the answers

What is the role of anhydrous CaCl₂ in the purification of hydrogen gas?

To absorb moisture. Signup and view all the answers

Which step should be executed before collecting hydrogen gas to ensure purity?

Allow all air to escape from the apparatus. Signup and view all the answers

What should be the position of the thistle funnel during the preparation of hydrogen gas?

Below the level of the dilute acid. Signup and view all the answers

What is the immediate observable effect when zinc reacts with dilute hydrochloric acid?

Brisk effervescence and hydrogen gas evolution. Signup and view all the answers

What happens if hydrogen gas is collected while air is still present in the apparatus?

An explosive mixture may form. Signup and view all the answers

Study Notes

Preparation of Hydrogen - Laboratory Method

Reaction: Zinc + Dilute Hydrochloric Acid (or Sulphuric Acid) → Zinc Chloride + Hydrogen Gas
Reactants: Granulated zinc and dilute acid (hydrochloric or sulphuric)
Procedure: Place granulated zinc in a flat-bottomed flask. Add dilute acid slowly through a thistle funnel.
Purification: Impure hydrogen gas is passed through washer bottles containing different solutions to remove impurities (e.g., Arsine, Phosphine, Hydrogen Sulphide, NO₂, CO₂, SO₂). Impurities are absorbed by these specific solutions.
Precautions: Avoid leaks in the apparatus. Keep no naked flames near the apparatus, as hydrogen is flammable.
Collection: The hydrogen gas is collected by downward displacement of water.

Preparation of Hydrogen - Industrial Methods (Bosch Process)

Step 1 Reaction: Production of water gas (CO + H₂) by heating coke with steam at ~1000°C.
Reactants: Coke (carbon), Steam (H₂O)
Temperature: ~1000°C
Process: Heating coke with steam to produce water gas (CO and H₂).
Chamber: Special designed converter.
Step 2 Reaction: Reduction of steam to hydrogen by carbon monoxide.
Reactants: Water gas, Steam (excess).
Temperature: ~450°C
Catalysts: Iron (III) oxide (Fe₂O₃), Chromium Oxide (Cr₂O₃)
Process: Excess steam reacts with water gas over catalysts creating more hydrogen.
Step 3 Reaction: Separation of CO₂ and CO from the resulting mixture (to separate hydrogen.)
Process: Carbon dioxide and remaining carbon monoxide are removed from the water gas mixture. This can be done by:
- dissolving the mixture in water under pressure
- using caustic potash solution (KOH)
- using an ammoniacal copper chloride solution

Uses of Hydrogen

Hydrogenation Reactions: Adds H₂ to organic compounds in the presence of a catalyst—e.g., vegetable oils to semi-solid fats. Hydrogenation of coal occurs under high pressure.
Extraction of Metals: Used to reduce metal oxides to free metals – a metallurgical process.
Welding and Cutting Metals: Hydrogen-oxygen mixture produces extremely high heat for welding and cutting metals.

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Description

This quiz explores the various methods of hydrogen preparation, focusing on both laboratory techniques using zinc and dilute acids, as well as industrial methods like the Bosch process. Learn about the reactions, purification processes, and safety precautions required in hydrogen production. Perfect for chemistry enthusiasts looking to deepen their understanding of hydrogen preparation methods.