redox Flashcards
1
Q
what is an oxidation number ?
A
- indicates how many electrons that an elements has gained or lost when it bond to another atom
2
Q
what’s the oxidation number of an uncombined element such as C, H, O2?
A
- 0
3
Q
what’s the oxidation number of oxygen in peroxides ?
A
- -1
4
Q
what’s the oxidation number of combined hydrogen such as NH3. H2S ?
A
- +1
5
Q
what’s the oxidation number of hydrogen in metal hydrides such as LiH?
A
- -1
6
Q
what’s the oxidation number of a simple ion?
A
- charge on the ion
e.g —> Na+ —> +1 ; Cl- —> -1
7
Q
what’s the oxidation number of combined fluorine such as NaF, CaF2?
A
- -1
8
Q
when an element has more than 1 stable oxidation number how is it indicated ?
A
- written as a roman numeral.
9
Q
what are oxyanions?
A
- anions (negative ions) made of two elements , one of which is oxygen.
10
Q
define oxidation.
A
- a process in which a species loses one or more electrons - also defines as increase in oxidation state of an element .
- gain of elections, a decrease in oxidation number
11
Q
WORKED EXAMPLE - work out oxidation numbers of each element in magnesium sulfate , MgSO4 ?
A
- sulfate ions have -2 charge so Mg must have a +2 charge to form a neutral ionic compound
- O is always -2 but we have 4 thus total; -8 for oxygen.
- S must be +6 as whole molecule needs add to 0
12
Q
what is a reduction ?
A
- process which species gains one or more electrons
- defined as decrease in oxidation state for an element
13
Q
what is an oxidising agent ?
A
- an element or compound that gained electrons from a reducing agent which itself loses electrons
14
Q
what is a redox reaction?
A
- reactions which oxidation and reduction both takes place .
- one species is oxidised while another is reduced .
15
Q
what’s the oxidation number of a metal?
A
- 0 as if is an uncombined element .
