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28 Cards in this Set
- Front
- Back
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Redox reactions |
transfer of electrons |
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For oxidation states |
+ loss of electrons - gain of electrons |
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Atom in free (uncombined) element have an oxidation state of |
0 |
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in simple ions, the oxidation state is |
the sam as the charge of the ion |
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The oxidation of all atoms in a neutral compound |
must add up to 0 |
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the oxidation states of all atoms in a polyatomic ion |
must add up to the charge of the ion |
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the usual oxidation state for an element |
is the same as its charge on it smost common ion |
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execptions to oxidation states |
oxyegn can be +1 when in a peroxide hydrogen can be -1 when in a hydride |
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As an element's oxidaiton state becomes more positive |
it is being oxidized |
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As an element's oxidation state becomes more negative |
it is being reduced |
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Steps in redox equations |
1) assign oxidation states 2) write half-equations for oxidation and reduction -balance atoms other than H and O -balance each half reaction for O by adding H₂O -balance each half reaction for H by adding H⁺ -add OH⁻ for each H in base solutions -balance each half reaction for charge by adding electrons to more positive side -check that each side is balance for atoms and charge 3) Equalize the # of electrons in 2 half-reactions by multiplying 4) Add half-equations together |
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one being reduced is |
oxidizing agent |
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one being oxidized is |
reducing agent |
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more reactive metals |
lose electrons more readily making them stronger reducing agent |
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you can tell if one metal is more reactive if |
a displacement reaction occurs |
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more reactive non-metals |
are stronger oxidizing agents |
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redox titration |
redox reaction between oxidizing agent and reducing agent electrons are transferred from reducing agent to oxidizing agent |
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Molarity formula |
mol of solute/liter of solution |
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Electrochemical cell |
two types voltaic (galvanic cells) electrolytic cells |
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Voltaic cell |
generate electricity from spontaneous redox reactions put two metals each in a half cell with its own solution of ions electrode potential- charge separation |
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electrolytic cell |
drive non spontaneous reactions using external source of electrical energy used battery to pump electrons into the electrolytic cell to drive redox reactions electric current passes through electrolyte; redox occurs at electrodes which removes the charge on ions and forms products electrically neutral ions are discharged cations attracted to negative cathode; anions attracted to positive anodes |
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electrolyte |
liquid (or solution of) ionic compund |
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other |
be able to write oxidation numbers and half-equations understand cell potential |
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oxidation |
loss of electrons e⁻ in products |
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reduction |
gain of electrons e⁻ in reactants |
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iron w/ manganate |
purple to colorless 5Fe²⁺ + MnO⁴⁻ + 8H⁺ → 5Fe³⁺ + Mn²⁺ + 4H₂O |
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iodine-thiosulfate reaction |
deep blue to colorless (in the presence of starch) OCl⁻ + 2I⁻ + 2H⁺ → I₂ + Cl⁻ + H₂O I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O₆ |
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Winkler Method |
measures dissolved oxygen in water 2Mn²⁺ + O₂ + 4OH⁻ → 2MnO₂ + 2H₂O MnO₂ + 2I⁻ + 4H⁺ → Mn²⁺ + I₂ +2H₂O I₂ + 2S₂O3²⁻ → 2I⁻ + S₄O₆²⁻ |
