Chemical Equations

• What is essential to know in order to progress in chemistry?

  You need to know about chemical equations.
• How are chemical changes represented?

  Chemical changes are shown using chemical equations.
• What is a word equation in chemistry?

  A word equation describes a chemical reaction using words instead of symbols.
• Write the word equation for the combustion of methane.

  Methane burns in oxygen giving carbon dioxide and water.
• What do symbol equations show in a chemical reaction?

  Symbol equations show the symbols or formulae of the reactants and products.
• What is the symbol equation for the reaction of magnesium and oxygen?

  2Mg + O₂ → 2MgO
• Why must symbol equations be balanced?

  There must always be the same number of atoms on both sides of the equation.
• How do you balance a chemical equation?

  You balance the equation by putting numbers in front of the formulae where needed.
• What should you do if you find an unbalanced element in a chemical equation?

  You should pencil in a number to try and balance it out.
• In the equation H₂SO₄ + NaOH → Na₂SO₄ + H₂O, how do you balance the hydrogen atoms?

  Change H₂O to 2H₂O.
• After adjusting the hydrogen atoms in the equation H₂SO₄ + NaOH → Na₂SO₄ + 2H₂O, what should you do next?

  You should adjust the sodium on the left side to 2NaOH.
• What is the importance of practice in balancing equations?

  Balancing equations is all about practice to become proficient.
• What do state symbols indicate in a chemical equation?

  State symbols indicate the physical state of a substance.
• What are the state symbols used in chemical equations?

  (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous.
• Write the balanced symbol equation for the reaction of hydrochloric acid and sodium carbonate.

  2HCl(aq) + Na₂CO₃(s) → 2NaCl(aq) + H₂O(l) + CO₂(g).
• What is an ionic equation?

  An ionic equation includes only the reactive particles and the products they form.
• How do you write an ionic equation from a balanced chemical equation?

  You break the reactants and products into ions and remove the spectator ions.
• In the ionic equation CaCl₂(aq) + 2NaOH(aq) → Ca(OH)₂(s) + 2NaCl(aq), which ions are spectator ions?

  Na⁺ and Cl⁻ ions are spectator ions.
• What do half equations show in chemical reactions?

  Half equations show how electrons are transferred during reactions.
• What does e⁻ represent in half equations?

  e⁻ stands for one electron.
• Write the half equation for sodium losing an electron to become a sodium ion.

  Na → Na⁺ + e⁻.
• Write the half equation for two hydrogen ions gaining electrons to form a hydrogen molecule.

  2H⁺ + 2e⁻ → H₂.
• How do you combine half equations to create full ionic equations?

  You combine them so that the electrons cancel out in the reactants and products.
• What should full ionic equations never contain?

  Full ionic equations never contain electrons.
• Write the full ionic equation for the sodium/hydrogen example given.

  2Na + 2H⁺ → 2Na⁺ + H₂.
• Why is practice important for half equations?

  Practice is important because half equations can be complex and require understanding of electron transfer.
• What are the steps to write an ionic equation?

  1. Break reactants and products into ions.
  2. Identify and remove spectator ions.
  3. Write the remaining ions as the ionic equation.
• What are the key components of balancing chemical equations?

  • Ensure the same number of atoms on both sides.
  • Use coefficients to balance the equation.
  • Do not change the chemical formulas.
• What are the types of equations discussed in the study material?

  • Word equations
  • Symbol equations
  • Ionic equations
  • Half equations
• What is the significance of state symbols in chemical equations?

  • Indicate the physical state of substances:
  • (s) = solid
  • (l) = liquid
  • (g) = gas
  • (aq) = aqueous
• What is the role of half equations in chemical reactions?

  • Show the transfer of electrons.
  • Used in oxidation and reduction reactions.