Oxidation-Reduction reactions Flashcards
what is oxidation?
a loss of electrons
what is reductions?
gain of electrons
what is an oxidizing agent?
it facilitates the oxidation of another compound and is reduced itself in the process. commonly electronegative.
What is a reducing agent?
it facilitates the reduction of another compound and is itself oxidized in the process. Commonly metal ions or hydrides
how does one assign oxidation numbers?
knowing the oxidation states of representative elements
any free element or diatomic species has an oxidation number of …?
zero
the oxidation number of a monatomic ion is equal to the ..?
Charge of the ion
When in compound, group IA metals have a ox number of … and Group IIA has an ox number of …?
1+ and 2+
When in compound, Group VIIA elements have an oxidation number of..?
-1 unless combined with an element with higher electronegativity
The ox state of hydrogen is…?
1+ unless it is paired with a less electronegative element, in which case it is -1
The ox state of oxygen is usually..?
-2 except peroxides (when its charge is -2) or in compound with more electronegative elements
The sum of oxidation numbers of all the atoms present in a compound is equal to the overall charge of ….
the compound
What is the half reaction, or ion-electron method?
- separate the two half reactions
- balance the atoms of each half-reaction. Start with all the elements besides H and O. In acidic solution, balance H and O using water and H+. In basic solution, balance the H and O using water and OH-
- balance the charges of each half-reaction by adding electrons as necessary to one side of the reaction
- multiply the half-reactions as necessary to obtain the same number of electrons in both half reactions
- add the half-reactions, canceling out terms on both sides of the reaction arrow
- confirm that the mass and charge are balanced
What is a complete ionic equation?
it accounts for all of the ions present in a reaction. To write a complete ionic reaction, split all aqueous compounds into their relevant ions. Keep solid salts intact .
What is the net ionic equation?
ignore spectator ions to focus only on the species that actually participate in the reaction. to obtain a net ionic reaction, subtract the ion appearing on both sides of the reaction, which are all spectator ions.
- solutions with no aqueous salts, net equation is generally the sam as balanced
- for double displacement (metathesis) reactions that do not form a solid salt, there is no net ionic reaction because all ions remain in solution and do not change ox number
What are disproportionation (dismutation) reactions?
are a type of redox reaction in which one element is both oxidized and reduced, forming at least two molecules containing the element with different ox states
what are oxidation-reduction titrations
the are similar in methodology to acid-base titrations. These titrations follow transfer of charge
-indicators used in such titrations change color when certain voltages of solutions are achieved.
What is a potentiometric titration?
is a form of redox titration in which a voltmeter or external cell measure the electromotive force (emf) of a solution. No indicator is used, and the equivalence point is determined by a sharp change in voltage.
What is the formal charge?
assumes equal division of electrons in bonds, awarding one electron to each atom in the bond, oxidation number is different and awards unevenly .
