Acids and Alkalis
- What is the pH range of strong acids? What is the pH range of weak alkalis?
- Name two common laboratory acids and their chemical formulas.
- Describe a simple test to identify carbon dioxide gas.
- Write a balanced chemical equation for the reaction between hydrochloric acid and sodium hydroxide.
- Using the universal indicator color chart, what color would you expect a solution of pH 9 to be?
- Why is it important to dilute concentrated acids before use?
- Explain how antacids work to relieve indigestion (heartburn).
Chemical Changes
- List three observable signs that may indicate a chemical change has taken place.
- Is dissolving sugar in water a physical or chemical change? Explain your reasoning.
- Explain the difference between exothermic and endothermic reactions, providing one example of each.
- Describe the chemical reaction that causes iron to rust. What conditions are needed for rusting to occur?
- A student reacts magnesium metal with hydrochloric acid. How could they measure the rate of this reaction?
- Explain why fireworks exploding is an example of a chemical change.
Secondary 2 Normal Academic Science Examination Topics: Acids and Alkalis & Chemical Changes Duration: 1.5 Hours Instructions:
- Answer all questions.
- Write your answers clearly in the spaces provided.
- All written responses must be in complete sentences.
Total Marks: 100
Section A: Multiple Choice Questions (1 mark each) Choose the correct answer from the options provided.
- Which pH value represents a neutral solution?
- A) 3
- B) 7
- C) 11
- D) 14
- What does an acid taste like?
- A) Sweet
- B) Bitter
- C) Sour
- D) Salty
- Which gas is most commonly produced when an acid reacts with a metal?
- A) Oxygen
- B) Hydrogen
- C) Nitrogen
- D) Carbon dioxide
- A base turns red litmus paper to:
- A) Red
- B) Blue
- C) Green
- D) It does not change color
- The reaction between an acid and a base produces:
- A) Salt and water
- B) Water and carbon dioxide
- C) Salt and hydrogen gas
- D) Hydrogen gas and carbon dioxide
(Continue this section with up to 20 items.)
Section B: Structured Questions (5 marks each) Answer the following questions.
- Explain what is meant by the term “pH scale” and describe what the scale measures.
- Provide the balanced chemical equation for the reaction between sulfuric acid (H2SO4) and sodium hydroxide (NaOH).
- Describe a laboratory experiment to determine whether a solution is acidic or basic using litmus paper. Include the expected outcomes for both types of solutions.
- What is a neutralization reaction? Give one example, including the reactants and products.
- Discuss the chemical changes that occur when iron rusts, including the reactants and products.
Section C: Practical Questions (10 marks each) Provide detailed answers and, where necessary, chemical equations.
- A student observed that when magnesium ribbon is added to hydrochloric acid, a gas is produced and the magnesium disappears. Describe what is happening in terms of a chemical reaction, and write the balanced chemical equation for this reaction.
- Design an experiment to show how temperature affects the rate of a reaction between calcium carbonate and hydrochloric acid. Include a hypothesis, materials needed, procedure, and how you would record your results.
- Explain how you could use the concept of conservation of mass to predict the mass of products in a reaction where zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas.
- Describe an exothermic reaction and an endothermic reaction. Give one example of each and explain how you can tell the difference between these two types of reactions based on energy changes.
- What is a displacement reaction? Provide an example and the corresponding chemical equation. Explain why the reaction happens in terms of reactivity.
Section D: Essay Question (15 marks) Write a detailed answer.
- Discuss the environmental impact of acid rain. Describe how acid rain is formed, its effects on the environment, and possible measures to mitigate these effects.