8,9 - Acids & Base, Redox Flashcards
oxidation number of elements (eg.O2, Cl2, N2)
0
oxidation number of ions (eg.Zn2+, Cl-)
same as their charge
G1 metals have oxidation state of
+1
G2 metals have oxidation state of
+2
O has oxidation state of
-2
except in peroxides (e.g. H2O2), where it is −1
H has oxidation state of
+1
except in certain metal hydrides (e.g. NaH), where it is −1
F and Cl have oxidation state of
-1
the sum of oxidation number in a compound is
0
in a compound/ion, the negative oxidation number is always given to
the more electronegative element
oxidizing agent
gets reduced (gains electrons)
= ox.no. decrease
reducing agent
gets oxidized (lose electrons)
= ox.no. increases
transition metals are characterized by
having variable oxidation states
more reactive metals act as
reducing agents (get oxidized, lose electrons to less reactive metal ions)
more reactive metals can do what to less reactive metals?
displace less reactive metals from their compounds (more reactive metals like to be in ion form!)
In redox titrations, an ____ is titrated against a ____
oxidizing agent
is titrated against
reducing agent
How is endpoint indicated in the Manganate(VII) Titrations?
purple color disappears
How is endpoint indicated in the **Iodine-Thiosulfate ** Titrations?
- light brown of the iodine turns paler as it is converted to colorless iodide ions
- add starch to clarify endpoint → blue/black
The Winkler Method is used to measure
concentration of dissolved oxygen in freshwater systems
Voltaic cells: what materials should the external connection and salt bridge be made of? why?
- external: metallic wire; to allow electron to flow
- salt bridge: aqueous electrolyte; to allow ions to flow
Electrolysis happens when
flow of current causes ionic compound to split up and form new substances
applications of electrolysis
- purifying copper
- plating metals with silver/gold
- extracting reactive metals (eg. Al)
electrolyte is
the substance passed by current and splits up
What happens to ions during electrolysis?
- -ions move to the anode → lose e-
- +ions move to the cathode → gain e-
- Electrically neutral molecules are released