ES 2 Flashcards
What happens to reducing agents in chemical reactions?
They are oxidized
Half equation for reduction
Cl2 + 2e- —> 2Cl-
Half equation for oxidation
2Br- -> Br2 + 2e-
What does oxidation mean?
- Gain of oxygen
- Loss of electrons
- An increase in oxidation number
What does reduction mean?
- Loss of oxygen
- Gain of electrons
- Decrease in oxidation number
What does the oxidation state of an element tell you?
How many electrons have been lost or gained compared to the unreacted element
What is the oxidation state for an atom in an element? Eg. O2, Mg, Cl2
0
How do you work out the oxidation states of the elements in a compound?
Oxidation states of all the elements must add up to 0 if the compound has no overall charge
- Some elements have oxidation states which never change
Oxidation state of flourine
-1
Oxidation state of oxygen in a compound
-2 (except when combined with F)
Oxidation state of chlorine in a compound
-1 (except when combined with O or F)
Oxidation state of bromine in a compound
-1 (except when combined with Cl, O or F)
Which element will retain its oxidation state in a compound?
The more reactive element
What is the oxidation state of iodine in a compound?
-1 (except when reacted with F, O, Cl, Br)
What is the oxidation state of hydrogen in a compound?
+1 (except in a metal hydride eg, NaH)
What is the oxidation state of a group one element in a compound?
+1
What is the oxidation state of a group 2 element in a compound?
+ 2
What is the oxidation state of a group 3 element in a compound?
+3
What do the oxidation states add up to in PO4 3-?
-3
How to work out systematic names
1) identify the name of the compound
2) work out the variable the element which has a variable oxidation state
3) work out its oxidation state
4) place the oxidation number in Roman numerals next to the variable element
How to name an oxyanion
Place the oxidation number in Roman numerals in brackets after the -ate
Oxidation state on 2I-
Still -1
What does a decrease in oxidation state mean?
Reduced
