Decomposition Reactions - Key Ideas

What is a decomposition reaction?

• A reaction where two or more substances combine
• A reaction where a single compound breaks down into simpler substances
• A reaction that produces heat and light only
• A reaction where energy is not required

What is the general form of a decomposition reaction?

• AB → A + B
• A + B → AB
• AB → C + D
• A + B → C

Which of the following is NOT a typical sign of a decomposition reaction?

• Gas release
• Colour change
• Formation of a solid
• No energy input

What is required for a decomposition reaction to proceed?

• A catalyst
• Energy input such as heat, light, or electricity
• A strong acid
• No external energy

What type of decomposition occurs when heat is used to break down a compound?

• Electrolysis
• Thermal decomposition
• Catalytic decomposition
• Enzyme-mediated decomposition

What is produced when metal carbonates decompose upon heating?

• Metal and oxygen
• Metal oxide and carbon dioxide
• Metal hydroxide and water
• Metal and water

Which of the following is a specific example of thermal decomposition (requires heat to start)?

• The decomposition of calcium carbonate to calcium oxide and carbon dioxide
• The decomposition of baking soda to sodium carbonate, water, and carbon dioxide
• The decomposition of water into hydrogen and oxygen by electrolysis
• The digestion of starch into glucose

What observable sign is often seen during the decomposition of calcium carbonate?

• A color change (green to black) and bubbles produced

• Gas release with a green gas

• No visible signs
• Formation of a precipitate

How can the presence of carbon dioxide gas be tested?

• Using a lit splint
• Bubbling it through limewater
• Using a thermometer
• Watching for a color change in the solution

Which of the following is produced during the thermal decomposition of sodium hydrogen carbonate (baking soda)?

• Sodium carbonate, water, and carbon dioxide
• Sodium hydroxide and oxygen
• Sodium, water, and oxygen
• Sodium oxide and water