Understanding Chemical Equations

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

• The law of conservation of mass requires that the number of atoms for each element is equal on both sides of a balanced chemical equation.

• The law of conservation of mass states that mass can be created or destroyed in a chemical reaction.

• Balancing chemical equations is only necessary for reactions involving gases.

• The law of conservation of mass applies only to solid substances in a chemical reaction.

Balance the following equation: H2 + O2 → H2O.

• 2 H2 + O2 → 2 H2O

• H2 + 2 O2 → H2O2

• 2 H2 + O2 → H2

• H2 + O2 → H2O

Identify the type of reaction: 2Na + Cl2 → 2NaCl.

• Combination reaction

• Decomposition reaction

• Single displacement reaction

• Double displacement reaction

What are the four main types of chemical reactions?

• Synthesis, Decomposition, Single Replacement, Double Replacement

• Neutralization

• Photolysis

• Combustion

• Redox

Balance the equation: C3H8 + O2 → CO2 + H2O.

• C3H8 + 2 O2 → CO2 + H2O

• C3H8 + 4 O2 → 3 CO2 + 5 H2O

• C3H8 + 5 O2 → 3 CO2 + 4 H2O

• C3H8 + 3 O2 → 2 CO2 + 3 H2O

What is a synthesis reaction? Provide an example.

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

• A synthesis reaction occurs when two substances are mixed without any chemical change: NaCl + H2O.

• A decomposition reaction is the breakdown of water: 2H2O → 2H2 + O2.

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

Describe a decomposition reaction and give an example.

• An example of a decomposition reaction is the electrolysis of water, which produces hydrogen and oxygen gases.

• An example of a decomposition reaction is the combustion of methane, producing carbon dioxide and water.

• A decomposition reaction occurs when a substance is heated to form a new compound.

• A decomposition reaction combines two or more substances to form a single product.

How do you identify a single replacement reaction?

• A single replacement reaction occurs when two elements combine to form a compound.

• A single replacement reaction involves two compounds exchanging elements.

• A single replacement reaction is identified by one element replacing another in a compound.

• A single replacement reaction is characterized by the formation of a gas or precipitate.

Balance the following equation: Fe + O2 → Fe2O3.

• 2 Fe + O2 → Fe2O3

• 3 Fe + 2 O2 → Fe2O3

• 4 Fe + 2 O2 → 2 Fe2O3

• 4 Fe + 3 O2 → 2 Fe2O3

What distinguishes an exothermic reaction from an endothermic reaction?

• Exothermic reactions absorb energy; endothermic reactions release energy.

• Both exothermic and endothermic reactions release energy.

• Exothermic reactions do not involve energy changes; endothermic reactions do.

• Exothermic reactions release energy; endothermic reactions absorb energy.