redox reactions Flashcards
what is a redox reaction?
since an oxidation and reduction reaction always take place together, this combined process is called a redox reaction
in a redox reaction, what happens to oxygen?
oxidation=gains oxygen
reduction=loses oxygen
in a redox reaction, what happens to hydrogen?
oxidation=loses hydrogen
reduction=gains hydrogen
in a redox reaction, what happens to the electrons?
oxidation=loses electron(s)
reduction=gains electron(s)
in a redox reaction, what happens to the oxidation states?
oxidation=increase
reduction=decrease
what is an oxidising agent?
a substance that causes another substance to be oxidised. however, it reduces itself
what is a reducing agent?
a substance that causes another substance to be reduced. however, it oxidises itself
what is an oxidation state?
an oxidation state refers to the charge an atom of an element would have if it existed as an ion in a compound (even if its covalently bonded).
what is the oxidation state of free elements? and what are some examples of free elements?
0
eg. Mg Cl2
what is the oxidation state of simple ions? and what are some examples of simple ions?
the oxidation state of a simple ion is the same as the charge of the ion
eg. Na+=+1
O2-=-2
sum of oxidation states?
the sum of oxidation states of the atoms or ions in a compound add up to zero
what do the roman numerals in the name of a compound indicate?
it indicates the oxidation state of the transition element
eg. copper(II) sulfate= copper=+2
what is the charge for group 1 elements?
always +1
what is the charge for group II elements?
always +2
what is the charge for flourine?
always -1
what is the charge for oxygen?
usually -2
exceptions: H2O2 and OF2
what is the charge for hydrogen?
usually +1
exceptions: BH3 and metal hydrides: NaH, AlH3
what happens to a substance when its oxidation state increases?
the substance is oxidised
what happens to a substance when its oxidation state decreases?
the substance is reduced.
what can be determined through oxidation state changes?
oxidation state changes is the most accurate way to determine whether a substance is oxidised or reduced. hence, the chance of it being tested is the highest
what do we compare when identifying oxidation state changes?
we compare the same elements on both sides of the equation
how to test for presence of oxidising agent?
use potassium iodide
if present, colourless potassium iodide changes to brown
how to test for presence of reducing agent?
use acidified potassium manganate
if reducing agent is present, purple potassium manganate turns colourless.
