HighMarks

Oxygen preparation and properties — KCSE Chemistry

KCSE Chemistry · 81 practice questions · 4 syllabus objectives · 4 revision lessons

37 easy35 medium9 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 oxygen from hydrogen peroxide using MnO₂ as a catalyst

State the physical and chemical properties of oxygen and write equations for reactions with metals and non-metals

Describe the test for oxygen and state its industrial uses

Oxygen preparation and properties

Revision Notes

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

Laboratory Preparation of Oxygen

Oxygen can be prepared in the laboratory by decomposing hydrogen peroxide (H₂O₂) using manganese(IV) oxide (MnO₂) as a catalyst. The reaction can be summarized as follows:

Chemical Equation: 2 H₂O₂ (aq) → 2 H₂O (l) + O₂ (g)

Procedure:

  1. Place about 20 mL of hydrogen peroxide solution in a conical flask.
  2. Add a small amount (about 0.5 g) of manganese(IV) oxide (MnO₂) to the flask.
  3. Observe the reaction; oxygen gas will evolve, indicated by bubbling.
  4. Collect the oxygen gas by upward displacement of air in an inverted test tube.

Properties of Oxygen:

  • Oxygen is a colorless, odorless gas.
  • It supports combustion, meaning it helps substances burn.
  • It is slightly soluble in water.

This method is efficient and demonstrates the catalytic role of MnO₂, which speeds up the decomposition of hydrogen peroxide without being consumed in the reaction.

Key points to remember

  • Oxygen is prepared by decomposing hydrogen peroxide.
  • MnO₂ acts as a catalyst in the reaction.
  • The reaction produces water and oxygen gas.
  • Collect oxygen using upward displacement of air.
  • Oxygen supports combustion and is colorless.

Worked example

Describe the laboratory preparation of oxygen from hydrogen peroxide using MnO₂.

  • Mix 20 mL of H₂O₂ with 0.5 g of MnO₂.
  • Oxygen gas evolves, collect it by upward displacement of air.

Read all 4 Oxygen preparation and properties lessons free

Sign up free to unlock the full set of revision notes, all 81 practice questions with marking schemes, plus a personalised study plan that adapts to the topics you keep getting wrong.

More lessons in this topic

Lesson 2: Properties and Reactions of Oxygen

Objective: State the physical and chemical properties of oxygen and write equations for reactions with metals and non-metals

Oxygen is a vital element with distinct physical and chemical properties. Physical properties include:

  • Colorless, odorless gas at room temperature
  • Slightly soluble in water
  • Supports combustion.

Chemical properties include:

  • Highly reactive with metals and non-metals
  • Forms oxides when reacting with elements.

When oxygen reacts with metals, it typically forms metal oxides. For example:

  • Reaction with magnesium:
    • Equation: 2Mg + O₂ → 2MgO
    • This reaction produces magnesium oxide, which is a white solid.

When reacting with non-metals, oxygen can form various oxides. For example:

  • Reaction with carbon:
    • Equation: C + O₂ → CO₂
    • This reaction produces carbon dioxide, a colorless gas.

Understanding these properties and reactions is crucial for predicting the behavior of oxygen in different chemical contexts.

  • Oxygen is colorless and odorless at room temperature.
  • It supports combustion and is highly reactive.
  • Reacts with metals to form metal oxides.
  • Reacts with non-metals to form oxides.
  • Oxygen is essential for respiration and combustion.

State the reaction of oxygen with iron and write the equation.

  • Iron reacts with oxygen to form iron(III) oxide:
    • Equation: 4Fe + 3O₂ → 2Fe₂O₃.
Lesson 3: Testing for Oxygen and Its Uses

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

Oxygen is a vital element with several industrial applications. To test for oxygen gas, you can use a glowing splint method:

  1. Collect the gas in a test tube.
  2. Insert a glowing splint into the tube.
  3. If the splint reignites, oxygen is present. This is due to oxygen's ability to support combustion.

Industrial Uses of Oxygen:

  • Welding: Oxygen is used in oxy-acetylene torches for cutting and welding metals.
  • Medical Applications: It is supplied to patients with respiratory issues to aid breathing.
  • Water Treatment: Oxygen is used to promote the breakdown of organic matter in wastewater.
  • Steel Production: Oxygen is used in the blast furnace process to produce iron from iron ore.

Understanding these properties helps in appreciating oxygen's role in various processes.

  • The glowing splint test indicates the presence of oxygen.
  • Oxygen supports combustion, reigniting a glowing splint.
  • Industrial uses include welding, medical applications, and steel production.
  • Oxygen is essential in water treatment processes.

Describe the test for oxygen and state two of its industrial uses.

  • The test for oxygen involves inserting a glowing splint into a test tube of the gas; if it reignites, oxygen is present.
  • Industrial uses of oxygen include: 1) welding metals using oxy-acetylene torches, 2) supplying oxygen for medical patients.
Lesson 4: Preparation and Properties of Oxygen

Objective: Oxygen preparation and properties

Oxygen is a vital element in our atmosphere and is essential for life. It can be prepared in the laboratory through various methods, primarily by the decomposition of hydrogen peroxide (H₂O₂) or the heating of potassium chlorate (KClO₃).

Methods of Preparation:

  • Decomposition of Hydrogen Peroxide:
    • When manganese(IV) oxide (MnO₂) is added to hydrogen peroxide, it decomposes to produce oxygen and water.
    • Equation:
      2 H₂O₂ (aq) → 2 H₂O (l) + O₂ (g)
  • Heating Potassium Chlorate:
    • Upon heating, potassium chlorate decomposes to yield potassium chloride and oxygen.
    • Equation:
      2 KClO₃ (s) → 2 KCl (s) + 3 O₂ (g)

Properties of Oxygen:

  • Physical Properties:
    • Colorless, odorless, and tasteless gas.
    • Slightly soluble in water.
  • Chemical Properties:
    • Supports combustion; it reacts with most elements to form oxides.
    • Combines with metals to form metal oxides (e.g., iron + oxygen → iron(III) oxide).

Understanding these aspects of oxygen is crucial for both theoretical and practical chemistry.

  • Oxygen can be prepared by decomposing hydrogen peroxide.
  • Heating potassium chlorate also produces oxygen gas.
  • Oxygen is colorless, odorless, and supports combustion.
  • It reacts with metals to form metal oxides.

Describe how oxygen can be prepared using potassium chlorate.

  • Heat potassium chlorate (KClO₃) in the presence of a catalyst.
  • The reaction produces potassium chloride (KCl) and oxygen (O₂) gas.

Sample Questions

Read 3 questions and answers free. Sign up to access all 81 questions with full KNEC-style marking schemes and a personalised study plan.

1
easySHORT ANSWER3 marks

The study of gaseous elements is crucial in understanding their reactions and properties. In this context, consider the behavior of a specific metal when subjected to combustion in an oxygen-rich environment. (a) Describe the observation when iron filings is burned in oxygen or air. (1 mark) (b) Write the equation for the reaction. (1 mark) (c) State the nature (acidic/basic/neutral) of the product when dissolved in water. (1 mark)

Answer & marking scheme

Part (a) — 3 marks
Burns with a bright white/dazzling flame producing white ash/powder (MgO) (1 mk)
2
easySHORT ANSWER4 marks

In the context of laboratory experiments involving gaseous substances, understanding the collection methods for specific gases is crucial. The following questions explore the techniques used to gather oxygen gas and the underlying physical properties that make these methods effective. (a) State two methods of collecting oxygen gas in the laboratory. (2 marks) (b) Explain why each method is suitable by stating the relevant physical property of oxygen. (2 marks)

Answer & marking scheme

Part (a) — 4 marks
Method 1: Collection over water (downward displacement of water) (1 mk)
Method 2: Upward displacement of air (gas jar held upright) (1 mk)
3
easySHORT ANSWER3 marks

In a laboratory setting, various chemical reactions can be employed to generate gases for experimental purposes. Understanding the reagents and their corresponding reactions is essential for effective gas preparation and analysis. (a) Name two reagents, apart from hydrogen peroxide, that can be used to prepare oxygen gas in the laboratory. (2 marks) (b) Write the equation for the preparation of oxygen using one of the reagents named in (a). (1 mark)

Answer & marking scheme

Part (a) — 3 marks
Potassium manganate(VII) (KMnO₄) — decomposes on heating (1 mk)
Potassium chlorate(V) (KClO₃) — decomposes on heating with MnO₂ catalyst / sodium peroxide (Na₂O₂) with water (1 mk)
4

In the study of gases, understanding the characteristics and identification methods of various substances is essential. The following questions explore the properties of a specific gas and its reactions in different scenarios. (a) State the chemical test for oxygen gas. (1 mark) (b) A student collected a gas and tested it with a glowing splint. The splint was extinguished. Explain why this does not confirm the gas is nitrogen. (1 mark) (c) Name one other gas that relights a glowing splint. (1 mark)

+78 More Questions

Sign up free to access all 81 questions with marking schemes, track your progress, and get personalised recommendations.

Frequently asked questions

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

Oxygen preparation and properties covers Describe the laboratory preparation of oxygen from hydrogen peroxide using MnO₂ as a catalyst; State the physical and chemical properties of oxygen and write equations for reactions with metals and non-metals; Describe the test for oxygen and state its industrial uses, and more, all aligned to the official KNEC KCSE Chemistry syllabus.

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

HighMarks has 81 Oxygen 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 Oxygen preparation and properties for the KCSE exam?

Start with the revision notes on this page to refresh the core concepts, then work through the practice questions in increasing difficulty. Sign up for HighMarks to get a personalised study plan that adapts to the topics you keep getting wrong, plus mock exams, subject-wide practice, and detailed performance tracking. See pricing.

Why Practise Oxygen preparation and properties?

KNEC Aligned

Questions match the KCSE syllabus objectives and exam format exactly.

Detailed Marking Schemes

Every answer shows exactly what examiners award marks for.

Track Your Mastery

See your score improve as you practise and identify remaining gaps.

Related topics in KCSE Chemistry

Continue revising adjacent topics from the Chemistry syllabus.

Chemistry
Hydrogen preparation and properties
Chemistry
Preparation of salts
Chemistry
Water treatment and purification
Chemistry
Qualitative analysis
Chemistry
Gas laws
Chemistry
Acid-base titration
Previous topic
Air composition
Next topic
Combustion and rusting

More KCSE resources

Round out your Chemistry preparation with full mock exams, past papers, and every Chemistry topic in one place.

All Chemistry topics

Browse every Chemistry revision topic on HighMarks.

KCSE past papers

Years of past KCSE papers with worked answers.

KCSE mock exams

Full-length, timed mocks scored against KNEC-style rubrics.

KCSE practice questions

All KCSE practice questions across every subject.

Master Oxygen preparation and properties for KCSE

Sign up free to unlock all 81 questions, track your progress, and get a personalised study plan for Chemistry.