C3: REDOX Reactions Flashcards
what is a redox reaction?
type of chemical reaction which involves transfer of electrons between two chemical species
OIL RIG mnemonic means
Oxidation Is Los ; Reduction Is Gain
State the oxidation rules for the following
- atom in free uncombined state _______
- sum of the oxidation numbers of all the atoms or ions in a compound_____
- oxidation number of a monoatomic ion in an ionic compound___________
- oxidation number of hydrogen in a compound or polyatomic ion is (a)_____________ except in hydrides where it is (b)______________
- oxidation number of oxygen in a compound or polyatomic ion is (a)_____________ , except in peroxides where it is (b)______________
- the sum of the oxidation numbers of the atoms in a plyatomic ion is____________
- the elements in covalent compounds or polyatomic ions (a)______________ except (b)______________ and (c) __________
- 0
- 0
- same as the charge on the ion
- (a) +1 , (b) -1
- (a) -2, (b) -1
- the same as the charge on the ion
- (a)may vary, (b) hydrogen, (c) oxygen
an oxidising agent causes the oxidation number of an element in free or combined state to (1)__________ by causing it to (2)__________ electrons. the oxidising agent itself is (3)___________ because it (4) ___________ electrons in the process.
- increase
- lose
- reduced
- gains
a reducing agent causes the oxidation number of an element in free or combined state to (1)__________ by causing it to (2)__________ electrons. the reducing agent itself is (3)___________ because it (4) ___________ electrons in the process.
- decrease
- gain
- oxidised
- loses
A (1)___________ causes the oxidation number of an element in free or combined state to decrease by causing it to (2)__________ electrons. The (3)________ agent itself is (4)___________ because it loses electrons in the process.
- reducing agent
- gain
- reducing
- oxidised
A (1)___________ causes the oxidation number of an element in free or combined state to increase by causing it to (2)__________ electrons. The (3)________ agent itself is (4)___________ because it loses electrons in the process.
- oxidising agent
- lose
- oxidising
- reduced
examples of oxidising agents
- acidified potassium manganate(VII) solution
- acidified potassium dichromate(VI) solution
- aqueous iron(III) salts
- Sodium chlorate solution
- hot concentrated suphuric acid
- dilute or concentrated nitric acid
- oxygen
- chlorine
- magnesium oxide
examples of reducing agents
- potassium iodide solution
- aqueous iron(II) salts
- hydrogen sulfide gas
- concentrated hydrochloric acid
- hydrogen
- carbon
- carbon monoxide
- reactive metals
identify the oxidising and reducing agents
- acidified potassium dicromate(VI)
- CO
- H2
- O2
- oxidising
- reducing
- reducing
- oxidising
identify the oxidising and reducing agents
- H2S
- acidified KMNO4(aq)
- NaClO(aq)
- conc. HCL
- reducing
- oxidising
- oxidising
- reducing
identify the oxidising and reducing agents
- Fe3+(aq)
- Fe2+(aq)
- C
- Na
- oxidising
- reducing
- reducing
- reducing
identify the oxidising and reducing agents
- Ca
- Mg
- Ag
- HNO3(aq)
- H2SO4(l)
- reducing
- reducing
- oxdising
- reducing
identify the oxidising and reducing agents
- KI(aq)
- NaClO(aq)
- H2
- CO
- H+/K2Cr2O7(aq)
- Al
- reducing
- oxidising
- reducing
- reducing
- oxidising
- reducing
two substances that act as both oxidising and reducing agents
- SO2
- H+/H2O2(aq)
How to test for the presence of an oxidizing agent
Add it to a known reducing agent which will give a visible Color change when oxidized
How to determine if a substance is a reducing agent
Add it to unknown oxidizing agent which will give a visible color change when reduced
To determine if a substance is a reducing agent add it to a known (1) ______________ , most commonly (2)_________________ or 3) __________________
- Oxidizing agent 2. Acidified potassium manganate(VII) 3. Acidified potassium dichromate(VI)
To determine if a substance is an oxidizing agent add it to a known (1) ______________ , most commonly (2)_________________ or 3) __________________
- Reducing agent 2. Potassium iodide solution 3. Aqueous solution of iron(III) salt
how do redox reactions account for rusting?
moisture and oxygen react with iron and its alloy steel causing the iron to be oxidized to form hydrated iron(III) oxide (Fe2O3.xH2O)
chlorine bleaches contain (1)_____________ and oxygen bleaches contain (2)_____________ which are both (3)_____________ and will remove coloured stains by oxidising the coloured dyes to thier colourless forms.
- sodium chlorate(I) (NaClO)
- H2O2
- Oxidising agents
explain the browning of fruits and vegetables when they are cut
enzymes in the cells on the cut surfaces of the fruit or vegetable use the oxygen in the air to oxidise certain chemicals in the cells to brown compounds called melanins
enzymes in the cells on the cut surfaces of some fruits or vegetables use the (1)_____________ in the air to (2)____________ certain chemicals in the cells to brown compounds called (3)____________. This is an example of a (4) _____________
- oxygen
- oxidise
- melanins
- redox reaction
how is redox applied in preserving food
Sodium sulphite and sulphur dioxide are used as food preservatives due to their properties as reducing agents. they prevent spoilage by preventing oxidation and reduce melanins back to their colouress form
These 2 food preservatives, (1) ____________ and (2)__________ prevent wine spoilage by preventing its (3)______________ to (4)______________.
- sodium sulphite
- sulfur dioxide
- oxidation
- vinegar
These 2 food preservatives, (1) ____________ and (2)__________ prevent oxidation of (3)____________ in fruits and (4) ___________, thus preveting their spoilage
- sodium sulphite
- sulphur dioxide
- vitamin C
- fruit juices
identify the oxidising/reducing agent/s found in each
- CuSO₄ + Fe → Cu + FeSO₄
- CuO + H2 → Cu + H₂O
- CuSO₄ - oxidizing agent; Fe - reducing agent
- CuO - oxidizing agent; H2 - reducing agent
what substance is oxidised and what is the oxidising agent in the reactions below?
- Ca(s) + H₂SO₄(aq) → CaSO₄(aq) + H₂(g)
- Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
- Ca is oxidized by H₂SO₄(aq)
- Zn(s) is oxidised by H₂SO₄(aq)
What substance is reduced in this reaction?
- C₂H₄(g) + 3 O₂(g) → 2 CO₂(g) + 2 H₂O(g)
- Ca(s) + H₂SO₄(aq) → CaSO₄(aq) + H₂(g)
- Oxygen
- H2SO4(aq)
