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What's my number?
Redox or not?
Agents 007
OIL or RIG
Oxidised or reduced?
100

Describe oxidation in terms of oxygen, hydrogen, electrons and oxidation states.

Oxidation is gain of oxygen, loss of hydrogen, loss of electrons and increase in oxidation states.

200

What is the oxidation state of Fe in Fe2O3? Show your working. 

Let x rep the oxidation state of Fe

2x + 3(-2) = 0
x = +3

200

What happens when a magnesium when it becomes magnesium chloride, MgCl2? Explain.

(a) It gains oxygen.

(b) It loses 2 protons. 

(c) Its electronic configuration becomes (2,8,8).

(d) Its oxidation state increases.

No O is gained when Mg becomes MgCl2.
Mg loses 2 electrons, not protons. 
Its electronic configuration becomes (2, 8).
Its oxidation state increases from 0 in Mg to +2 in Mg2+.

300

What is the oxidation state of sulfur in sulfate ion, SO42-? Show your working. 

Let x rep the oxidation state of S

x + 4(-2) = -2
x = +6

300

Which of the following is NOT a redox reaction? Explain

(a) Mg + 2HCl → MgCl2 + H2

(b) MgO + 2HCl → MgCl2 + H2O

(c) Mg + H­2O → MgO + H2

(d) Ca + 2H2O → Ca(OH)2 + H2

b

b is a neutralisation reaction. 

This is not a redox reaction as there is no change in oxidation state in any of the elements.

300

A reaction took place between iron (II) sulfate and magnesium.

 FeSO4 (aq) + Mg (s) → MgSO4 (aq) + Fe (s)

Which substance is oxidised? Explain.

Mg is oxidised as oxidation state of Mg increases from 0 in Mg to +2 in MgSO4.

400

Hydrogen and copper (II) oxide react to produce copper metal and water.

CuO + H­2 → Cu + H2O

What are the oxidising and reducing agents in this reaction? Explain. 

CuO is reduced -> H2 is the reducing agent.
H2 is oxidised -> CuO is the oxidising agent.

400

In which of the following equations is the italicized substance reduced?

(a) Cl2 + 2I-→ 2Cl- + I2

(b) Zn + H2SO4 → ZnSO4 + H2

(c) 2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O

(d) CuO + H2 → Cu + H2O

d

CuO loses oxygen to form Cu or
oxidation state of copper decreases from +2 in CuO to 0 in Cu.