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Hydrogen preparation and properties — KCSE Chemistry

KCSE Chemistry · 71 practice questions · 4 syllabus objectives · 4 revision lessons

27 easy33 medium11 hard

Last updated · Aligned to the KNEC KCSE syllabus

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Describe the laboratory preparation of hydrogen from the reaction of zinc with dilute sulphuric acid

State the physical and chemical properties of hydrogen including its reaction with copper(II) oxide

Describe the test for hydrogen and state its industrial uses

Hydrogen preparation and properties

Revision Notes

Concise lesson notes for Hydrogen preparation and properties, written to the KCSE Chemistry marking standard. Read the first lesson free below.

Laboratory Preparation of Hydrogen

Hydrogen can be prepared in the laboratory by reacting zinc with dilute sulphuric acid. This reaction is a classic example of an acid-metal reaction. The process involves the following steps:

  1. Materials Required:

    • Zinc metal (Zn)
    • Dilute sulphuric acid (H₂SO₄)
    • Test tube
    • Delivery tube
    • Water trough or gas jar

  2. Procedure:

    • Place a small piece of zinc in a test tube.
    • Carefully add dilute sulphuric acid to the test tube containing zinc.
    • Observe the effervescence (bubbles) that occurs, indicating hydrogen gas is being produced.
    • Collect the hydrogen gas using a delivery tube leading to an inverted gas jar or water trough.

  3. Chemical Equation:

    • The reaction can be represented as:
      Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Properties of Hydrogen:

  • It is a colorless and odorless gas.
  • It is highly flammable and burns with a pale blue flame.
  • It can be tested using a lit splint, producing a 'pop' sound when ignited.

Key points to remember

  • Zinc reacts with dilute sulphuric acid to produce hydrogen.
  • Effervescence indicates hydrogen gas formation.
  • The reaction produces zinc sulfate as a byproduct.
  • Hydrogen is colorless, odorless, and flammable.

Worked example

Describe how hydrogen is prepared in the laboratory using zinc and dilute sulphuric acid.

  • Zinc is added to dilute sulphuric acid in a test tube.
  • Effervescence occurs, indicating hydrogen gas production.
  • The reaction equation is Zn + H₂SO₄ → ZnSO₄ + H₂.

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More lessons in this topic

Lesson 2: Properties and Reactions of Hydrogen

Objective: State the physical and chemical properties of hydrogen including its reaction with copper(II) oxide

Hydrogen is the simplest and most abundant element in the universe. Its properties can be categorized into physical and chemical.

Physical Properties:

  • Colorless, odorless, and tasteless gas at room temperature.
  • Low density: It is the lightest gas, making it rise in air.
  • Insoluble in water, but can dissolve in some organic solvents.
  • Highly flammable: Burns in air to form water.

Chemical Properties:

  • Reacts with oxygen to produce water (H₂ + O₂ → 2H₂O).
  • Reacts with metals to form metal hydrides.
  • Reduces metal oxides, such as copper(II) oxide.

When hydrogen reacts with copper(II) oxide (CuO), it reduces the oxide to copper and water:

Reaction: H₂ + CuO → Cu + H₂O

This reaction is significant in demonstrating hydrogen's reducing properties and is often used in laboratory settings to illustrate the reactivity of hydrogen. Understanding these properties is crucial for applications in industries and research.

  • Hydrogen is a colorless, odorless gas at room temperature.
  • It has low density and is highly flammable.
  • Hydrogen reduces metal oxides, forming metals and water.
  • The reaction with copper(II) oxide produces copper and water.

State the reaction of hydrogen with copper(II) oxide. H₂ + CuO → Cu + H₂O.

Lesson 3: Testing for Hydrogen and Its Uses

Objective: Describe the test for hydrogen and state its industrial uses

Hydrogen is a colorless, odorless gas that can be tested using a simple method. To test for hydrogen, bring a lit splint near the gas. If hydrogen is present, it will produce a 'pop' sound as it ignites. This is due to the rapid combustion of hydrogen in the presence of oxygen, forming water vapor.

Hydrogen has several important industrial uses:

  • Fuel: Hydrogen is used in fuel cells to produce electricity.
  • Manufacturing ammonia: In the Haber process, hydrogen combines with nitrogen to produce ammonia, essential for fertilizers.
  • Petroleum refining: Hydrogen is used to remove sulfur from fuels and to convert heavy hydrocarbons into lighter ones.
  • Hydrogenation: It is used in the food industry to convert unsaturated fats into saturated fats, improving shelf life.

Understanding these properties and uses of hydrogen is crucial for various scientific and industrial applications.

  • Hydrogen is tested by bringing a lit splint near the gas.
  • A 'pop' sound indicates the presence of hydrogen.
  • Hydrogen is used in fuel cells for electricity.
  • It is essential in the production of ammonia for fertilizers.
  • Hydrogen is used in petroleum refining and food processing.

Describe the test for hydrogen and state one industrial use.

  • Bring a lit splint near the gas; a 'pop' sound indicates hydrogen.
  • Hydrogen is used in fuel cells to produce electricity.
Lesson 4: Preparation and Properties of Hydrogen

Objective: Hydrogen preparation and properties

Hydrogen is a colorless, odorless gas and the lightest element in the periodic table. It can be prepared through several methods:

  • Electrolysis of water: Passing an electric current through water splits it into hydrogen and oxygen gases.

  • Reaction of acids with metals: For example, when hydrochloric acid reacts with zinc, hydrogen gas is produced:

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

  • Steam reforming: Reacting methane with steam produces hydrogen and carbon monoxide.

Properties of Hydrogen:

  • Physical properties: Hydrogen is less dense than air and is highly flammable.
  • Chemical properties: It reacts with oxygen to form water, releasing energy. It can also react with halogens to form hydrogen halides.

Understanding these methods and properties is crucial for various applications in industries, such as fuel cells and ammonia production.

  • Hydrogen is the lightest and simplest element.
  • It can be prepared via electrolysis and metal-acid reactions.
  • Hydrogen is flammable and forms water with oxygen.
  • Used in fuel cells and industrial processes.
  • Produced through steam reforming of methane.

Describe how hydrogen can be prepared using zinc and hydrochloric acid. \n- Zinc reacts with hydrochloric acid. \n- The reaction produces hydrogen gas and zinc chloride.

Sample Questions

Read 3 questions and answers free. Sign up to access all 71 questions with full KNEC-style marking schemes and a personalised study plan.

1
easySHORT ANSWER4 marks

In a laboratory setting, the generation and collection of gases are fundamental processes in chemistry. Consider the various techniques employed to capture hydrogen gas produced from the reaction of zinc with dilute sulphuric acid. (a) Identify two methods that can be used to collect hydrogen gas in the laboratory. (2 marks) (b) For each method, explain the physical property of hydrogen that makes it suitable. (2 marks)

Answer & marking scheme

Part (a) — 4 marks
Downward displacement of water (collection over water) (1 mk)
Upward delivery / downward displacement of air (inverted container) (1 mk)
2
easySHORT ANSWER3 marks

Define the test for hydrogen gas and give two industrial uses of hydrogen. (3 marks)

Answer & marking scheme

Part (a) — 1 mark
A glowing splint will produce a 'pop' sound when hydrogen is present (1 mk)
Part (b) — 2 marks
Used in the production of ammonia through the Haber process (1 mk)
Used as a fuel in hydrogen fuel cells (1 mk)
3
easySHORT ANSWER4 marks

State the products formed when hydrogen reacts with copper(II) oxide and explain the significance of this reaction in metallurgy. (4 marks)

Answer & marking scheme

Part (a) — 2 marks
Copper is formed as a solid (1 mk)
Water (steam) is produced as a gas (1 mk)
Part (b) — 2 marks
The reaction reduces copper(II) oxide to copper, allowing for metal extraction (1 mk)
It provides a method to purify copper from its ores (1 mk)
4

Identify two physical properties of hydrogen gas that make it suitable for use in balloons. (2 marks)

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Frequently asked questions

What does the KCSE Chemistry topic "Hydrogen preparation and properties" cover?

Hydrogen preparation and properties covers Describe the laboratory preparation of hydrogen from the reaction of zinc with dilute sulphuric acid; State the physical and chemical properties of hydrogen including its reaction with copper(II) oxide; Describe the test for hydrogen and state its industrial uses, and more, all aligned to the official KNEC KCSE Chemistry syllabus.

How many practice questions are available for Hydrogen preparation and properties?

HighMarks has 71 Hydrogen preparation and properties practice questions for KCSE Chemistry, each with a full marking scheme. The first 3 are free; sign up to access the rest, plus all KCSE mock exams and past papers.

Are these aligned with the KNEC KCSE syllabus?

Yes. Every objective on this page is taken directly from the official KNEC KCSE Chemistry syllabus. Practice questions match the KCSE exam format and are graded against the standard KNEC marking scheme.

How should I revise Hydrogen preparation and properties for the KCSE exam?

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