General Chemistry Ch. 11 – Oxidation-Reduction Reactions

question

oxidation number rules
answer

  1. The oxidation number of a free element is zero
  2. the oxidation number for a monoatomic ion is equal to the charge of the ion
  3. The oxidation number of each Group IA element in a compound is +1
  4. The oxidation number of each Group IIA element in a compound is +2
  5. The oxidation number of each Group VIIA element in a compound is -1, except when combined with an element of higher electronegativity
  6. the oxidation number of hydrogen is usually +1; however, its oxidation number is -1 in compounds with less electronegative elements (Groups IA and IIA)
  7. In most compounds the oxidation number of oxygen is -2.
  8. The sum of the oxidation number of all the atoms  present in a neutral compound is zero. The sum of the oxidation numbers of the atoms present in a polyatomic ion is equal to the charge of the ion.

question

Balancing oxidation-reduction reactions
answer

  1. Separate the two half reactions
  2. Balance the atoms of each half reaction. Balance all atoms except H and O first. Then in acidic solution ad H2O to balance the O atoms and then add H+ to balance the H atoms. In basic solution, us OH and H2O to balance the O and H atoms
  3. Balance the charges of each half reaction by adding electrons
  4. Multiply the half reactions so that each half reaction has the same number of electrons so they will cancel out
  5. Add the half reactions and cancel out

question

net ionic equations
answer

ignore spectator ions to focus only the species that actually participate in the reaction.
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net ionic equations:

combination reactions

decomposition reactions

combustion reactions

double-displacement (metathesis) reactions

 

answer

all are oxidation reduction reactions except for double-displacement reactions that don’t form a solid salt. If no solid salt is formed there is no net ionic reaction because all species stay in solution and their oxidation number doesn’t change
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disproportionation reactions
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aka dismutation reactions – a type of redox reaction in which one element is both oxidized and reduced, forming at least two molecules containing the element with different oxidation states
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redox titrations
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use voltage as an indicator as opposed to pH like acid-base titrations
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potentiometric titration
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a form of redox titration in which a voltmeter or external cell measures the electromotive force (emf) of a solution. No indicator is used, and the equivalence point is determined by a sharp change in voltage

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