Understanding Chemical Equations

What is a chemical equation?

• A chemical equation is a graphical representation of molecules.

• A chemical equation represents a chemical reaction using symbols and formulas.

• A chemical equation describes physical properties of substances.

• A chemical equation is a mathematical formula.

Define reactants and products in a chemical reaction.

• Reactants are the starting materials; products are the substances formed.

• Reactants are the substances that disappear; products are the substances that remain unchanged.

• Reactants are the final products; products are the initial materials.

• Reactants are always gases; products are always liquids.

What does it mean to balance a chemical equation?

• To balance a chemical equation means to make sure that the number of atoms for each element is equal on both sides of the equation.

• Balancing a chemical equation involves adding more reactants to increase the reaction rate.

• To balance a chemical equation means to ensure that the total mass of the products is greater than that of the reactants.

• To balance a chemical equation means to change the chemical properties of the substances involved.

Write the balanced equation for the combustion of methane.

• CH4 + 3 O2 -> 2 CO2 + 2 H2O

• C2H6 + O2 -> CO2 + H2O

• CH4 + 2 O2 -> CO2 + 2 H2O

• CH4 + O2 -> CO + H2O

What is the Law of Conservation of Mass?

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

• Mass can be created or destroyed in chemical reactions.

• Mass can change depending on the temperature of the system.

• The Law of Conservation of Mass states that mass is conserved in a closed system during chemical reactions.

How do you identify a single displacement reaction?

• A single displacement reaction involves two compounds exchanging elements.

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

• A single displacement reaction occurs only in the presence of heat.

• A single displacement reaction is characterized by the formation of a gas.

Provide an example of a double displacement reaction.

• CaCO3 + HCl → CaCl2 + CO2 + H2O

• NaCl + AgNO3 → NaNO3 + AgCl

• H2 + O2 → H2O

• Na2SO4 + BaCl2 → BaSO4 + 2NaCl

What are the products of the reaction between an acid and a base?

• Carbon dioxide and water

• Hydrogen and oxygen

• Sodium and chlorine

• Water and salt

Explain the role of coefficients in balancing equations.

• Coefficients represent the temperature of a reaction.

• Coefficients are used to indicate the state of matter of substances.

• Coefficients determine the color of the substances in the equation.

• Coefficients indicate the relative amounts of substances in a balanced chemical equation.

What is the difference between a strong acid and a weak acid?

• Strong acids have a higher pH than weak acids.

• Weak acids do not conduct electricity in solution.

• Strong acids fully dissociate in solution; weak acids partially dissociate.

• Strong acids are always more concentrated than weak acids.