redox 1

• What does oxidation involve?

  Oxidation involves the loss of electrons.
• What does reduction involve?

  Reduction involves the gain of electrons.
• What acronym is used to remember the redox rule?

  The acronym is OILRIG (oxidation is loss, reduction is gain).
• What does the oxidation number indicate?

  The oxidation number indicates the oxidation state of an element or ionic substance.

  
• What are the rules for allocating oxidation numbers?

  • The oxidation number of an element is zero.
  • Oxidation numbers in a neutral compound add up to zero.
  • Oxidation numbers in a charged compound add up to the total charge.
  • Hydrogen has an oxidation number of +1.
  • Oxygen has an oxidation number of -2.
  • Halogens have an oxidation number of -1.
  • Group I metals have an oxidation number of +1.
  • Group II metals have an oxidation number of +2.

  
• What are the exceptions to the oxidation number rules?

  • Oxygen has an oxidation number of -1 in peroxides.
  • Hydrogen has an oxidation number of -1 in metal hydrides.
• How can the oxidation number of sulfur be determined in a compound?

  By using known oxidation numbers and setting up an equation to solve for sulfur's oxidation number.
• What does the oxidation number of sulfur equal in the example provided?

  The oxidation number of sulfur equals +6.
• How are Roman numerals used in oxidation states?

  Roman numerals indicate the oxidation number of an element with a variable oxidation state.
• What does Copper(II) sulphate indicate about copper's oxidation number?

  It indicates that the oxidation number of copper is +2.
• What does Iron(II) sulphate(VI) indicate about iron and sulfur's oxidation numbers?

  It indicates that the oxidation number of iron is +2 and the oxidation number of sulfur is +6.
• How can oxidation numbers be used to deduce the formula of compounds?

  • Oxidation numbers help determine the ratio of elements in a compound.
  • The overall charge of the compound must be considered.

  
• How are elements arranged in the periodic table?

  Elements are arranged by proton number and their orbitals.
• What is the significance of orbitals in the periodic table?

  • Orbitals correspond with blocks on the Periodic Table.
  • Each element in a block has outer electrons in the same type of orbital.
• What patterns in oxidation number can be observed in the periodic table?


  • s block elements (groups 1 and 2) generally lose electrons and form positive oxidation numbers.
  • p block non-metals generally gain electrons and form negative oxidation states.

  
• What is the role of an oxidising agent in a redox reaction?

  An oxidising agent accepts electrons and is reduced.
• What is the role of a reducing agent in a redox reaction?

  A reducing agent donates electrons and is oxidised.
• What characterizes redox reactions?

  • Oxidation and reduction occur simultaneously.
  • One species loses electrons while another gains them.
• What is a disproportionation reaction?

  A disproportionation reaction is when a species is both oxidised and reduced.
• What happens to the oxidation state of chlorine in the example of its reaction with cold water?

  The oxidation state of chlorine goes from 0 to +1 and -1.

  
• What are half equations used for in redox reactions?

  • Half equations show the separate oxidation and reduction reactions.
  • They must be balanced in terms of species and charges.

  
• What is the method for balancing half equations?

  1. Balance all species excluding oxygen and hydrogen.
  2. Balance oxygen using H2O.
  3. Balance hydrogen using H+ ions.
  4. Balance charges using e- (electrons).

  
• What must be true for half equations to be combined in a redox reaction?

  The number of electrons must be the same for both half equations.
• What should be done after combining half equations in a redox reaction?

  • The electrons should be cancelled out on each side of the equation.
• What is the definition of oxidation number?


  The charge of an ion or a theoretical charge of an atom in a covalently bonded compound assuming the bond becomes ionic.
• What happens during oxidation in a chemical reaction?

  There is a loss of electrons and an increase in oxidation number.
• What is reduction in terms of electron transfer?

  Reduction is the gain of electrons and a decrease in oxidation number.
• What does the term redox refer to?

  A reaction that involves both oxidation and reduction.
• What is the role of an oxidising agent in a redox reaction?

  An oxidising agent accepts electrons and gets reduced.
• What does a reducing agent do in a redox reaction?

  A reducing agent donates electrons and gets oxidised.
• What are half-equations in the context of redox reactions?

  • A full redox equation can be split into two half-equations: oxidation and reduction.
  • Useful for balancing complex redox reactions.
• How can the redox reaction involving permanganate and oxalate ions be split into half-equations?

  Reduction: $2 \text{MnO}_4^- +$$16 \text{H}^+$$+$$10 \text{e}^- \rightarrow 2 \text{Mn}^{2+} +$$8 \text{H}_2\text{O}$ and Oxidation: $5 \text{C}_2\text{O}_4^{2-} \rightarrow 10 \text{CO}_2 +$ 10 \text{e}^-\.
• What is the balanced redox equation for the reaction involving permanganate and oxalate ions?

  $2 \text{MnO}_4^- +$$5 \text{C}_2\text{O}_4^{2-} +$$16 \text{H}^+$$\rightarrow 2 \text{Mn}^{2+} +$$5 \text{CO}_2 +$$8 \text{H}_2\text{O}$
• What is disproportionation in a redox reaction?

  A redox reaction involving an element in a single species being simultaneously oxidised and reduced.
• Give an example of a disproportionation reaction.


  $\text{Cl}_2 +$$\text{H}_2\text{O} \rightleftharpoons \text{HClO} +$$\text{HCl}$