oxidation-reduction

In the reaction
2Ca(s) + O₂(g) --> 2CaO(s), calcium is __________

• Reduced
• Synthesized
• Oxidized
• None of the above

     In the reaction Zn + H₂O --> ZnO₂ + H₂
 which element, if any, is oxidized? 

• Zinc
• Hydrogen
• Oxygen
• None

What is the oxidation number of Nitrogen in HNO₃

• -7

• -5

• +5

• +7

• +2

Find the oxidation number of S in S₂O₄ ^2-

• +3

• +6

• -6

• -3

• -4

Identify the species reduced in the following reaction.

Fe_(s) + 2 Ag⁺_(aq) → Fe²⁺_(aq) + 2 Ag_(s)

• Fe

• Ag

• none of these

• None of the above

What is the oxidation number of: Br₂?

• -1

• +1

• -2

• 0

What is the oxidation number of Sr⁺²?

• -2

• 0

• +2

• +1

What is the oxidation number of chlorine in ClO₃^- ?

• -1

• +1

• -1

• +5

Determine the oxidation number of the selected element in each ion/ compound.

a) N in N₂O₄

b) Cr in CrO₄ ^2-

c) I in IO₃^-

• +8, -6, +5

• +2, +8, +6

• +4, +6, +5

• -4, -6, -5

• -4, -8, -6

What is the oxidation number of O in CO₂?

• +2
• -1
• +4
• -2