C3.1 Introducing chemical reactions

• What is the topic of C3 in the study material?

  Chemical reactions
• What section discusses the formulae of elements and molecules?

  C3.1.1
• What is the focus of the learning outcome in C3.1.1?

  Writing the formulae of metal and non-metal elements
• What is the formula for iodine?

  I2
• What is the formula for neon?

  Ne
• What is the purpose of using the Periodic Table in writing formulae?

  To help identify the symbols and charges of elements
• What is the focus of C3.1.2?

  Formulae of ionic compounds
• What should students be able to do after studying C3.1.2?

  Write the formulae for ionic compounds
• What is the law of conservation of mass?

  The mass of reactants equals the mass of products in a chemical reaction
• Why might the mass seem to change during some reactions?

  Because gases may escape in an open container
• How do you calculate the mass of oxygen gained in a reaction?

  By subtracting the mass of the reactants from the mass of the products
• What happens to copper carbonate when heated?

  It decomposes to form copper oxide and carbon dioxide
• What is the formula for sulfuric acid?

  H2SO4
• What are balanced equations used for?

  To show the conservation of mass in a chemical reaction
• What is the first step in writing a balanced equation?

  Write the correct formulas for the reactants and products
• What do state symbols indicate in a chemical equation?

  The physical state of the reactants and products
• How do half equations relate to ionic equations?

  Half equations show the changes in oxidation states during a reaction
• What is a mole defined as?


  The amount of substance that contains as many entities as there are atoms in 12g of carbon-12
• How can you measure a mole of a substance?

  By using its molar mass in grams
• How do you calculate the stoichiometry of a reaction?

  By using the coefficients from the balanced equation
• What is a limiting reactant?

  The reactant that is completely consumed in a reaction
• How do you calculate the mass of hydrogen needed to produce ammonia?

  By using the stoichiometric ratios from the balanced equation
• What are the steps to balance a chemical equation?

  1. Write the correct formulas for the reactants and products.
  2. Count the number of atoms of each element on both sides.
  3. Adjust coefficients to balance the number of atoms.
  4. Ensure that the equation is balanced in terms of mass and charge.
• What are the differences between half equations and full ionic equations?

  • Half equations show the oxidation or reduction of a single species.
  • Full ionic equations show all species involved in the reaction.
  • Half equations focus on electron transfer, while full ionic equations focus on mass and charge balance.
• What is the significance of the mole in chemistry?

  • It provides a bridge between the atomic scale and macroscopic quantities.
  • It allows chemists to count particles by weighing them.
  • It is essential for stoichiometric calculations in reactions.
• How do you calculate the mass of a reactant needed for a reaction?

  1. Write the balanced equation for the reaction.
  2. Determine the molar masses of the reactants.
  3. Use stoichiometric ratios to find the required mass.
  4. Calculate using the formula: mass = moles × molar mass.
• What is the role of the Periodic Table in writing chemical formulae?

  • It provides the symbols for elements.
  • It indicates the charges of ions.
  • It helps in determining the ratios of elements in compounds.
• How does the law of conservation of mass apply to chemical reactions?

  • Mass is neither created nor destroyed in a chemical reaction.
  • The total mass of reactants equals the total mass of products.
  • This principle is fundamental for balancing chemical equations.