Chemical Reactions and Phase Changes

This lesson covers reversible reactions, contrasting them with irreversible ones using examples like the combustion of magnesium. It demonstrates the thermal decomposition of ammonium chloride, explaining the process and its reversibility. The lesson also addresses the common misconception of confusing decomposition with sublimation, clarifying the differences between phase changes and chemical reactions.

Which of the following is an example of an irreversible reaction?

• Dissolving sugar in water

• Boiling water

• Melting ice

• Frying an egg

What does the reaction arrow in a reversible reaction indicate?

• The reaction is fast

• The reaction is irreversible

• The reaction is slow

• The reaction can proceed in both directions

What are the products of the thermal decomposition of ammonium chloride?

• Sodium and chlorine

• Water and carbon dioxide

• Magnesium and oxygen

• Ammonia and hydrogen chloride

Why should the thermal decomposition of ammonium chloride be conducted in a fume cupboard?

• To ensure even heating

• To prevent the loss of heat

• To avoid contamination

• To protect from corrosive gases

What color does red litmus paper turn in the presence of ammonia?

• Red

• Blue

• Yellow

• Green

What is a common misconception about the thermal decomposition of ammonium chloride?

• It is a combustion reaction

• It is a sublimation reaction

• It is a neutralization reaction

• It is a precipitation reaction

What phase change is incorrectly associated with the decomposition of ammonium chloride?

• Melting

• Sublimation

• Condensation

• Freezing

What happens to a substance during sublimation?

• It changes from solid to liquid

• It changes from gas to liquid

• It changes from solid to gas

• It changes from liquid to gas

What is the main difference between sublimation and decomposition?

• Sublimation involves a phase change without chemical change

• Decomposition involves a physical change

• Sublimation involves a chemical change

• Decomposition involves a phase change without chemical change

What does ammonium chloride decompose into when heated?

• Sodium and chlorine

• Magnesium and oxygen

• Ammonia and hydrogen chloride

• Water and carbon dioxide