Redox

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1. Which would be the best oxidising agent?
A. N2O
B. NH4Cl
C. NO2
D. HNO3
Answer
D. HNO3
The nitrogen is in the highest state of +5. Hence it can easily undergo reduction, and hence behave as an oxidising agent.
2. Consider the reaction where ClO3-1 becomes Cl-1 , the chlorine :
A. takes up 6 electrons
B. takes up 4 electrons
C. is unchanged
D. takes up 7 electrons
Answer
A. takes up 6 electrons
The Cl in ClO3-1 is +5.
It takes up 6e- to become Cl-1
3. What is the charge of each aluminium ion in aluminium oxide? Answer
+3
The formula for aluminium oxide is Al2O3.
Each O is -2 hence -6 in total.
Thus the Al is +6, which shows that each Al is +3
4. Does a reducing agent gain or lose electrons? Answer
lose electrons
A reducing agent itself undergoes an oxidation ½ reaction. Hence it loses electrons.
5. In the following incomplete reaction, the Fe2+ ion is an oxidising agent.
What is X most likely?
A. Fe
B. Fe2+
C. Fe3+
D. Fe4+
Answer
Fe
Since the Fe2+ ion is an oxidising agent, it must undergo a reduction ½ reaction.
6. Is H2SO4 most likely to be an oxidising agent or a reducing agent? Answer
oxidising agent
The S is in the +6 state and easily undergoes reduction. Hence the molecule is an oxidising agent.
7. What is meant by a “redox” reaction? Answer
A type of reaction that involves a transfer of electrons.
8. What is the charge of mercury in:
mercury (ii) oxide?
Answer
+2
The Roman Numeral (ii) refers to the charge of the substance in front of it.
Hence Hg+2
9. Why can redox reactions be used to create electricity? Answer
Redox reactions involve a transfer of electrons. Indirect transfer of electrons such as in the Voltaic Cell, produces useful electricity.
10. What redox role does ammonia play in this reaction?

NH3 + O2 → NO + H2O

Answer
Reducing Agent
The N in ammonia changes from -3 to +2 in NO
This is oxidation. Hence ammonia is a reducing agent.

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