Chapter 7

Balancing Reactions

• Ionic reactions and equations
  • ionic compounds are held together as solids electrostatic interactions
  • ionic compounds dissociate in water
    • solvated ions move around independently in solution

Solubility, Net ionic Reactions

• molecular equation displays discrete compunds
• complete ionic equations displays all individual ions in equation
• net ionic equation displays all individual ions in equation
  • spectator ions do not directly participate in reactions
• precipitation reactions
  • occurs when a non-soluble solid crashes out of solution
  • steps
    • identify reactant ions
    • identify possible products
      • ions that form solids have a net neutral charge
      • most ionic materials only contain two types of ions
        • one anion and one cation
• Solubility rules: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjiy7ij3JjfAhUNJt8KHYEwCIYQjRx6BAgBEAU&url=https%3A%2F%2Fsdsuchem200.com%2F2018%2F08%2F26%2Fsolubility-rules%2F&psig=AOvVaw0YesRjI4Cuk3SyHGZAfAVW&ust=1544650117466775

Acid/Base Reactions

• occur when a proton is transferred from one species to another
• Acids dissolved in water form hydronium
  • strong acids completely form hydronium
  • weak acids partially form hydronium
• Bases dissolved in water form hydroxide
  • strong bases completely form hydroxide
  • weak bases partially form hydroxide
• neutralization reaction
  • specific acid-base reaction in which an acid reacts with a base

REDOX Reactions and Balancing

• an abundance of reactions involve the transfer of electrons that are categorized as oxidation-reduction reactions
• oxidation - loss of electrons
• reduction - gain of electrons
• do not necessarily involve ions or ionic species
• oxidation states
  • the charge its atoms would possess if the compound was ionic 
  • Steps
    • Oxidation state of an atom in an elemental substance is zero
    • the oxidation state of a monatomic ion is equal to its charge
    • Oxidation states for common non-metals are as follows:
      • Hydrogen: +1 when combined with non-metals and -1 when combined with metals
      • Oxygen: -2 in most compounds, sometimes -1 (peroxides), and -1 when combined with metals
      • Halogens: -1 for F always, -1 for other halogens unless combined with O or other more EN halogens
    • the sum of oxidation numbers for all atoms in a molecule or polyatomic ion equals the charge on the molecule or ion
• Characteristics of Redox reactions
  • transfer or electrons
  • sometimes forms ionic substances, other times it occurs in a formal sense
  • oxidant/oxidizing agent = species that is reduced
  • reductant/reducing agent = species that is oxidized
• half reactions
  • separate the oxidation from the reduction for analysis purposes
• Balancing Redox Reactions
  • Acidic conditions
    • Steps
      • Write separate equations for the oxidation and reduction half reactions
      • For each half-reaction
        • balance all elements except H and O
        • Balance O using water
        • Balance H using H+
        • Balance charge using e-
      • Balance half-reaction charge, if necessary. Multiply one or both half-reactions by integers to equalize the number of e- transferred in the two half reactions
      • Combine both half-reactions into a complete equation, then cancel identical species
      • Finally, check to be sure the element and charges balance 
  • Basic conditions
    • same as acidic conditions with a few extra steps
    • add the same amount of OH- as H+ on both sides

Reaction Stoichiometry

• involves a quantitative assessment of the relationships between the amounts of substances consumed and produced by the reaction
• must use a balanced equation
• coefficients are used to derive stoichiometric factors
• https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwj_96Kj4JjfAhVmUd8KHf9rBDoQjRx6BAgBEAU&url=https%3A%2F%2Fwww.onlinemathlearning.com%2Fstoichiometry.html&psig=AOvVaw2xY9g_KIEzOj53CaihngTs&ust=1544651199649109

Limiting Reagent

• the quantities of the products are limited by the reagent present in the least quantity

Reaction Yield in Percent

• the limiting reagent for a given chemical reaction determines the maximum quantity of a product that is possible to form
• the reaction yield is an indication of the reaction's efficiency
• percent yield = actual yield/theoretical yield