Understanding Chemical Reactions

What are the four main types of chemical reactions?

• Photolysis

• Redox

• Neutralization

• Synthesis, Decomposition, Single Replacement, Double Replacement

• Combustion

Define a synthesis reaction and provide an example.

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

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

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

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

What is the difference between a decomposition reaction and a single replacement reaction?

• A decomposition reaction replaces elements in a compound; a single replacement reaction forms new compounds.

• A decomposition reaction breaks down a compound; a single replacement reaction involves an element replacing another in a compound.

• A decomposition reaction involves two compounds reacting; a single replacement reaction breaks down a compound.

• A decomposition reaction combines elements to form a compound; a single replacement reaction does not involve any compounds.

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

• 2 H2 + O2 -> 2 H2O

• 2 H2 + O2 -> H2

• H2 + O2 -> H2O

• H2 + 2 O2 -> H2O2

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

• The total mass remains constant in chemical reactions.

• Mass is only conserved in physical changes.

• The total mass increases during a reaction.

• Mass can be created in chemical reactions.

Describe what happens in an acid-base reaction.

• An acid absorbs a proton from a base, creating carbon dioxide.

• An acid donates a proton to a base, resulting in water and a salt.

• An acid and a base combine to form only a gas without any other products.

• A base donates a proton to an acid, resulting in ammonia and water.

What is the pH scale and what does it measure?

• The pH scale measures the temperature of a solution.

• The pH scale indicates the color of a solution.

• The pH scale measures the density of a solution.

• The pH scale measures the concentration of hydrogen ions in a solution.

Provide an example of a neutralization reaction.

• H2SO4 + KOH → K2SO4 + H2O

• CaCO3 + HCl → CaCl2 + CO2 + H2O

• HCl + NaOH → NaCl + H2O

• NaCl + H2O → Na + Cl2

How do you identify an acid and a base in a chemical equation?

• Acids are always liquid; bases are always solid.

• Acids absorb H+ ions; bases absorb OH- ions.

• Acids donate H+ ions; bases donate OH- ions.

• Acids and bases both donate electrons.

What role do catalysts play in chemical reactions?

• Catalysts speed up chemical reactions by lowering activation energy.

• Catalysts change the products of the reaction to create new substances.

• Catalysts are consumed in the reaction and do not affect the outcome.

• Catalysts slow down chemical reactions by increasing activation energy.