Understanding Chemical Reactions

What are the four main types of chemical reactions?

• oxidation, reduction, hydrolysis, combustion

• synthesis, polymerization, neutralization, precipitation

• decomposition, fermentation, crystallization, evaporation

• synthesis, decomposition, single replacement, double replacement

Define a synthesis reaction and provide an example.

• The displacement of zinc by copper: Zn + CuSO4 → ZnSO4 + Cu.

• An example of a synthesis reaction is the formation of water: 2H2 + O2 → 2H2O.

• The decomposition of water: 2H2O → 2H2 + O2.

• The combustion of methane: CH4 + 2O2 → CO2 + 2H2O.

What is the general form of a decomposition reaction?

• AB -> A + B

• A + B -> AB

• A + B -> C

• AB + C -> A + B + C

Explain what a combustion reaction is and give an example.

• An example of a combustion reaction is the rusting of iron.

• Combustion reactions only occur in solid materials.

• An example of a combustion reaction is the burning of methane: CH4 + 2O2 → CO2 + 2H2O.

• A combustion reaction is the process of photosynthesis.

What distinguishes a single displacement reaction from a double displacement reaction?

• Single displacement reactions require heat; double displacement reactions do not require any energy change.

• Single displacement reactions involve two elements exchanging places; double displacement reactions involve one compound breaking down.

• Single displacement reactions occur only in gases; double displacement reactions occur in liquids.

• Single displacement reactions involve one element displacing another; double displacement reactions involve the exchange of ions between two compounds.

How do you balance the chemical equation H2 + O2 → H2O?

• H2 + O2 → H2O

• H2 + O2 → 2 H2O

• 2 H2 + 2 O2 → 2 H2O

• 2 H2 + O2 → 2 H2O

What is the law of conservation of mass in relation to chemical equations?

• Mass can be created or destroyed in a chemical reaction.

• The mass of reactants is always greater than the mass of products.

• The total mass of reactants equals the total mass of products in a chemical reaction.

• The total mass of products is irrelevant to the reactants.

Describe an exothermic reaction and provide an example.

• Rusting of iron

• Combustion of hydrocarbons (e.g., burning wood or gasoline)

• Photosynthesis in plants

• Dissolving salt in water

What is an endothermic reaction? Give an example.

• Photosynthesis is an example of an endothermic reaction.

• Respiration in animals

• Combustion of gasoline

• Dissolving salt in water

How can you identify a redox reaction?

• A redox reaction is characterized by the absorption of light energy.

• Redox reactions can be identified by the color change of the reactants.

• A redox reaction involves only the formation of new compounds.

• A redox reaction is identified by changes in oxidation states and the transfer of electrons between species.