Chemical Equations

• Why do equations need to be balanced?

  Because matter cannot be created nor destroyed
• What do symbol equations use to show atoms?

  Chemical symbols
• How is the Haber process represented in a chemical equation?

  N$_2$(g) + H$_2$(g) → NH$_3$(g)
• What do the left and right sides of a chemical equation represent?

  Left: reactants; Right: products
• What is wrong with the equation N$_2$(g) + H$_2$(g) → NH$_3$(g)?


  It is not balanced
• How do you balance the equation for the Haber process?

  N$_2$(g) + 3H$_2$(g) → 2NH$_3$(g)
• What is the issue with the equation HNO$_3$(aq) → H$_2$O(l) + NO$_2$(g) + O$_2$(g)?


  It is not balanced
• How do you balance the decomposition of nitric acid?

  2HNO$_3$(aq) → H$_2$O(l) + 2NO$_2$(g) + ½O$_2$(g)
• What is the significance of treating groups of atoms like OH in equations?

  They remain unchanged in reactions
• How is the reaction between iron sulfate and sodium hydroxide represented?

  FeSO$_4$(aq) + 2NaOH(aq) → Fe(OH)$_2$(s) + Na$_2$SO$_4$(aq)
• What is the problem with the equation FeSO$_4$(aq) + NaOH(aq) → Fe(OH)$_2$(s) + Na$_2$SO$_4$(aq)?


  It is not balanced
• What do ionic equations summarize?

  Reactions involving ions in solution
• How is the reaction between nitric acid and sodium hydroxide represented in ionic form?

  H⁺ + OH^- → H₂O
• What is the purpose of removing spectator ions in ionic equations?

  To simplify the equation
• What is the net ionic equation for the reaction of barium nitrate and sodium phosphate?

  3Ba²⁺ + 2PO₄³⁻ → Ba₃(PO₄)₂
• How are equations used in calculating reacting masses?

  They provide ratios between substances
• How do you calculate the mass of magnesium oxide produced from magnesium?

  Use the equation: 2Mg + O$_2$ → 2MgO
• What is the first step in calculating the mass of magnesium oxide from magnesium?

  Calculate the Ar of magnesium
• How do you calculate the number of moles of magnesium?

  Divide mass by Ar (6 ÷ 24)
• What is the relationship between moles of magnesium and moles of magnesium oxide?

  0.25 moles of Mg produces 0.25 moles of MgO
• How do you calculate the mass of 0.25 moles of magnesium oxide?

  Mass = moles × Ar (0.25 × 40)
• What is the Ar of iron?

  55.8
• How do you calculate the number of moles of iron from 14 grams?

  14 ÷ 55.8 = 0.251 moles
• How many moles of iron are needed to produce iron (III) oxide?

  0.251 moles of Fe produces 0.125 moles of Fe₂O₃
• How do you calculate the mass of 0.125 moles of iron (III) oxide?

  Mass = moles × Ar (0.125 × 159.6)
• How can the ideal gas equation be used in reactions?

  To calculate the volume of gas produced
• How do you calculate the volume of hydrogen gas produced from sodium and water?

  Use the equation: 2Na + 2H₂O → 2NaOH + H₂
• What is the first step in calculating the volume of hydrogen gas produced?

  Calculate the Ar of sodium
• How do you calculate the moles of sodium from 30 grams?

  30 ÷ 23 = 1.3 moles
• What is the ratio of sodium to hydrogen gas in the reaction?

  2:1
• How do you calculate the volume of hydrogen gas produced?

  Volume = nRT ÷ p
• What is the gas constant (R) value used in calculations?

  8.31 J/K/mol
• What is the standard temperature in Kelvin for gas calculations?

  298 K
• What is the pressure unit used in the ideal gas equation?

  Pascals (Pa)
• What are the steps to balance a chemical equation?

  1. Identify reactants and products
  2. Count atoms of each element
  3. Adjust coefficients to balance
  4. Ensure same number of atoms on both sides
• What are the steps to calculate reacting masses using a balanced equation?

  1. Calculate Ar of reactants
  2. Calculate moles of reactants
  3. Use mole ratios to find moles of products
  4. Calculate mass of products using moles and Ar
• What is the ideal gas equation and its components?

  • Equation: PV = nRT
  • P = pressure (Pa)
  • V = volume (m³)
  • n = number of moles
  • R = gas constant (8.31 J/K/mol)
  • T = temperature (K)