Redox

Traps in Redox

• Reverses a trend, direction or effect
  State the rule with its direction before looking at the options (down group 1 reactivity INCREASES; exothermic forward reaction: heating shifts LEFT). An option that is the mirror image of the rule is the trap.
• Chooses a true but irrelevant statement
  Re-read the question word (why, which, what causes). A true fact that answers a different question is still wrong.
• Oxidation/reduction definition errors
  OIL RIG: Oxidation Is Loss of electrons, Reduction Is Gain. The oxidising agent is itself reduced. Oxidation number increases on oxidation.
• Picks a related substance or process with a different role
  Learn reagents and processes as one-line 'name → job' cards and contrast neighbours in a table (process | product | catalyst | conditions). Match the job in the stem, not just the topic.
• Oxidation number errors
  Sum of oxidation numbers = overall charge. O is usually −2, H is +1 (except in metal hydrides), group 1 metals +1.
• Ignores or misapplies a subscript or bracket
  A subscript multiplies only the atom before it; a subscript after a bracket multiplies everything inside. Expand the formula into a full atom list before adding masses.
• Mixes up a pair of similar chemical terms
  Keep a list of confusable pairs with one defining feature each and a hook. Underline the key word in the stem and check it against the definition, not the sound of the name.
• Miscounts atoms, electrons or steps
  After working, check by counting back: total electrons = atomic number; atoms in the formula match the subscripts; number of half-lives = time ÷ half-life.