Lesson Note on Sulphur: Compounds, Contact Process and Uses of H2SO4 for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Third Term
Week: 2
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Non-metals and their Compounds
Previous Lesson: Sulphur: Meaning, Electronic Structure, Allotropy and Uses.
Topic: SULPHUR
Subject Matter: Compounds of sulphur, industrial preparation of H2SO4 (contact process), uses of H2SO4

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• List at least three common compounds of sulphur.
• Describe the contact process for the industrial preparation of sulphuric acid.
• State at least five uses of sulphuric acid.

Affective Domain:

• Appreciate the industrial importance of sulphuric acid.
• Recognize the safety precautions required when handling concentrated acids.

Psychomotor Domain:

• Draw and label a simple flow diagram of the contact process.
• Identify samples of sulphuric acid.

Social Domain:

• Participate in discussions about industrial applications of chemistry.
• Understand the impact of chemical industries on society.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio
• https://www.google.com/search?q=chemistry+sss2+sulphur+compounds
• https://www.google.com/search?q=contact+process+for+sulphuric+acid

Instructional Materials

The teacher will teach this lesson with the aid of:

• Chart on contact process for preparation of H2SO4
• H2SO4 (car battery acid) sample
• Matches

Rationale for the Lesson

This lesson helps pupils understand the various compounds formed by sulphur and the crucial industrial method for producing sulphuric acid. Understanding the uses of sulphuric acid enables pupils to appreciate its importance in various industries and daily life.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of the properties of sulphur, basic chemical reactions, and the concept of catalysts.

Lesson Content/Board Summary

SULPHUR

Compounds of Sulphur

Sulphur forms several important compounds, both with metals and non-metals. These compounds exhibit various chemical properties and have diverse applications.

Common compounds of sulphur include:

• Sulphur dioxide (SO2): A colourless gas with a pungent smell, used in food preservation and as a bleaching agent.
• Sulphur trioxide (SO3): A colourless solid, an intermediate in the production of sulphuric acid.
• Hydrogen sulphide (H2S): A poisonous gas with a rotten egg smell, often found in natural gas and petroleum.
• Sulphuric acid (H2SO4): A strong mineral acid with many industrial uses.

Industrial Preparation of Sulphuric Acid (Contact Process)

The Contact Process is the most common industrial method for producing sulphuric acid (H2SO4). It involves several stages to ensure a high yield of the acid.

The overall process can be summarized in three main stages:

1. Production of Sulphur Dioxide (SO2): Sulphur is burnt in air, or sulphide ores (e.g., iron pyrites, FeS2) are roasted in air to produce SO2 gas.
2. Catalytic Oxidation of Sulphur Dioxide to Sulphur Trioxide (SO3): SO2 is reacted with oxygen in the presence of a catalyst to form SO3.
3. Absorption of Sulphur Trioxide to form Oleum, then Dilution to Sulphuric Acid: SO3 is absorbed in concentrated H2SO4 to form oleum, which is then diluted with water to produce sulphuric acid.

Detailed Steps of the Contact Process:

1. Burning of Sulphur:

   Sulphur is burnt in a furnace in a current of dry air to produce sulphur dioxide gas.

   Equation: S(s) + O2(g) → SO2(g)

2. Purification of Sulphur Dioxide:

   The SO2 gas is cooled and passed through purifiers to remove impurities like dust, arsenic compounds, and moisture. Impurities can poison the catalyst.

3. Catalytic Oxidation:

   The purified SO2 gas is mixed with more air (O2) and passed over a catalyst, usually Vanadium(V) oxide (V2O5), at a temperature of 400-450°C and a pressure of 1-2 atmospheres. This reaction is exothermic and reversible.

   Equation: 2SO2(g) + O2(g) ⇌ 2SO3(g) (ΔH = -197 kJ/mol)

   Note: Platinum was an older catalyst but is more expensive and easily poisoned.

4. Absorption of Sulphur Trioxide:

   The sulphur trioxide (SO3) gas is then absorbed in concentrated sulphuric acid (98%) to form oleum (H2S2O7), also known as fuming sulphuric acid. This method is preferred over absorbing SO3 directly in water because direct absorption produces a fine mist of H2SO4 which is difficult to condense.

   Equation: SO3(g) + H2SO4(l) → H2S2O7(l)
5. Dilution of Oleum:

   The oleum is then carefully diluted with the required amount of water to produce concentrated sulphuric acid (98% H2SO4).

   Equation: H2S2O7(l) + H2O(l) → 2H2SO4(l)

Uses of Sulphuric Acid (H2SO4)

Sulphuric acid is a highly important industrial chemical, often referred to as the “King of Chemicals” due to its wide range of applications.

Some major uses of sulphuric acid include:

• Fertilizer production: Used to make ammonium sulphate, superphosphate, and other phosphate fertilizers.
• Petroleum refining: Used to purify petroleum and remove impurities.
• Manufacture of detergents and soaps: Used in the sulphonation process.
• Production of other chemicals: Used to make hydrochloric acid, nitric acid, and various sulphates.
• Dyestuffs and pigments: Used in the manufacture of paints, dyes, and pigments.
• Explosives: Used in the production of some explosives like nitroglycerine.
• Metallurgy: Used in pickling (cleaning) of metals before electroplating or galvanizing.
• Car batteries: Used as the electrolyte in lead-acid batteries.
• Dehydrating agent: Due to its strong affinity for water, it is used as a drying agent.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and reminds them of the previous lesson on sulphur. The teacher then ignites a matchstick and asks pupils to identify the smell produced, linking it to sulphur compounds.
Pupils’ Activity: Pupils respond to the greeting, recall the previous lesson, and identify the smell of sulphur dioxide.
Learning Point: Pupils are engaged and connect previous knowledge to the new topic.

Step 2: Compounds of Sulphur

Time: 5 minutes
Teaching Skill: Explanation/Listing
Teacher’s Activity: The teacher introduces various compounds of sulphur, such as sulphur dioxide, hydrogen sulphide, and sulphuric acid, and briefly discusses their occurrence and importance.
Pupils’ Activity: Pupils listen attentively and take notes on the compounds mentioned.
Learning Point: Pupils identify different compounds of sulphur.

Step 3: Overview of Contact Process

Time: 8 minutes
Teaching Skill: Explanation/Questioning
Teacher’s Activity: The teacher introduces the Contact Process as the industrial method for producing sulphuric acid, explaining the raw materials and the overall aim. The teacher asks pupils if they know any industrial processes.
Pupils’ Activity: Pupils listen, answer questions, and prepare for the detailed explanation of the process.
Learning Point: Pupils understand the purpose and raw materials of the Contact Process.

Step 4: Detailed Steps of Contact Process

Time: 10 minutes
Teaching Skill: Explanation/Diagrammatic representation
Teacher’s Activity: The teacher uses the chart on the contact process to explain each stage in detail, including the reactions, conditions (temperature, pressure, catalyst), and reasons for each step (e.g., why SO3 is absorbed in H2SO4 and not water).
Pupils’ Activity: Pupils observe the chart, listen to the explanation, ask questions, and take notes on the process steps and equations.
Learning Point: Pupils grasp the chemical principles and stages involved in the Contact Process.

Step 5: Drawing the Contact Process Flow Diagram

Time: 7 minutes
Teaching Skill: Demonstration/Guidance
Teacher’s Activity: The teacher guides pupils on how to draw and label a simple flow diagram of the contact process, emphasizing key components like the furnace, purifier, catalytic converter, and absorption tower. The teacher may draw a simplified version on the board.
Pupils’ Activity: Pupils draw and label the contact process flow diagram in their notebooks under the teacher’s guidance.
Learning Point: Pupils develop a visual understanding of the industrial setup.

Step 6: Uses of Sulphuric Acid

Time: 5 minutes
Teaching Skill: Discussion/Listing
Teacher’s Activity: The teacher leads a discussion on the various uses of sulphuric acid, showing the sample of car battery acid and explaining its role. The teacher encourages pupils to suggest other uses they might know.
Pupils’ Activity: Pupils contribute to the discussion, list uses of sulphuric acid, and observe the sample.
Learning Point: Pupils recognize the wide applications of sulphuric acid in industries and daily life.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. List three compounds of sulphur.
2. Outline the main stages of the Contact Process for H2SO4 production.
3. What catalyst is used in the Contact Process?
4. State four uses of sulphuric acid.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of sulphur compounds and the industrial significance of sulphuric acid. The teacher assigns homework: “Draw a fully labeled diagram of the contact process and list five safety precautions when handling concentrated H2SO4.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

• Sulphur – A non-metallic chemical element with atomic number 16.
• Sulphuric Acid (H2SO4) – A strong mineral acid, also known as oil of vitriol.
• Contact Process – The industrial method for producing sulphuric acid.
• Sulphur Dioxide (SO2) – A gas produced by burning sulphur, an intermediate in H2SO4 production.
• Sulphur Trioxide (SO3) – A gas formed from SO2 and O2, absorbed to make oleum.
• Catalyst – A substance that speeds up a chemical reaction without being consumed (e.g., Vanadium(V) oxide).
• Oleum (H2S2O7) – Fuming sulphuric acid, formed by dissolving SO3 in concentrated H2SO4.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional questions on the environmental impact of sulphur industries or ask them to research other industrial uses of sulphur compounds. For those needing more support, the teacher will provide simplified diagrams and allow peer-tutoring during drawing activities.

Note for teachers using this lesson plan

Ensure all safety precautions are strictly followed when demonstrating with concentrated sulphuric acid. Emphasize the economic importance of the Contact Process to Nigeria. Encourage pupils to relate the lesson to real-world applications and industries in their locality.