Physical Science _ T1 _ L7 _ EXAM QUESTIONS - Zoom

Introduction

  • Morning greetings to students

  • Teacher discussing current flu and urging students to turn on their cameras.

Tasks and Class Structure

  • Importance of completing Task 28 promptly.

  • Today's class focused on exam questions related to Lesson Seven, following previous content from six lessons.

  • Recording of the lesson will be available for review after class.

Class Activities

Starting the Exam Questions

  • Students given five minutes to begin working on Question Two.

  • Emphasis on trying to understand even confusing parts of the questions.

  • Encouragement for students to ask questions via chat if needed.

Investigation of Reactions

Objective of Investigation

  • Determine which salts react spontaneously with zinc metal:

    • Salts: Copper Sulfate, Magnesium Sulfate, Silver Nitrate, Barium Chloride.

    • Zinc as the metal for reactions.

  • Basic rule: Salts higher or lower than zinc on the reactivity table dictate reactivity.

Understanding the Reactivity Table

  • Zinc's position relative to other elements impacts its reactivity.

  • Salts above zinc (like Magnesium, Barium) will not react because they are more reactive.

  • Salts below zinc (like Copper, Silver) will react because zinc is stronger in terms of oxidation potential.

Practical Steps for Investigation

  1. Dissolve salts in distilled water.

  2. Clean zinc before immersing in solutions.

  3. After each test, clean zinc and repeat in next solution.

Exam Question Analysis

Question 2.2: Reactivity of Salts

  • Use the reactivity table to assess which salts react with zinc:

    • Identify copper and silver as salts that will be displaced by zinc.

    • Question: Identify ions produced in the reaction with zinc.

Question 2.3: Balanced Ionic Equations

  • Write balanced equations for reactions:

    • Zinc + Copper:

      • Zn (s) → Zn²⁺ + 2e⁻

      • Cu²⁺ + 2e⁻ → Cu (s)

    • Net ionic: Zn (s) + Cu²⁺ → Zn²⁺ + Cu (s)

    • Zinc + Silver:

      • Zn (s) → Zn²⁺ + 2e⁻

      • 2Ag⁺ + 2e⁻ → 2Ag (s)

    • Net ionic: Zn (s) + 2Ag⁺ → Zn²⁺ + 2Ag (s)

Question 2.4: Non-reactivity of Zinc

  • Explain non-reactivity:

    • Zinc does not react with more reactive salts (like Mg and Ba) because they are higher on the activity series, making them stronger oxidizing agents.

Rusting and Protection

Question 3: Rust Formation

  • Iron rusts due to the presence of air and water:

    • Rust equation: Iron + O₂ + H₂O → Iron(OH)₂ → iron oxide (rust).

  • Rust absence in deserts (lack of water) vs. presence in coastal areas.

Galvanization

  • Galvanization prevents rusting: Iron coated with zinc.

  • Zinc acts as a sacrificial anode, oxidizing instead of iron due to its position on the reactivity table, forming a protective layer of zinc oxide.

Chemical Reactions and Principles

Question 4: Phosgene Production

  • Phosgene (COCl₂) produced via the reaction:

    • CO + Cl₂ ⇌ COCl₂

  • Exothermic nature indicated by delta H < 0.

Maximizing Production with Le Chatelier's Principle

  • To increase phosgene production, lower temperature (favoring the exothermic forward reaction).

  • Delta H < 0 indicates exothermic reaction, with heat released.

Conclusion

  • Reminder for students to watch the recording for continued review on exam questions.

  • Anticipation of the new chapter on Electrochemistry starting next class.

  • Closing greetings and reminders for students.