Choose the correct answer for each question.

1. When the equation
   2MnO4 -    +   x H+    +    y Sn2+    =    y Sn4+    +    2Mn2+    +   x/2 H2O
   is balanced, y equals

   1.   ?    1
   2.   ?    2
   3.   ?    5
   4.   ?    8
   5.   ?    16

2. Iodide ions react with iodate ions in acid solution according to the following equation:
   5I^- +   IO₃^-   +   6H⁺   =   3I₂   +   3H₂O
   Which statement about this reaction is correct?
   

   1.   ?    The iodide ion loses electrons and is reduced.
   2.   ?    The oxidation number of iodine in the iodate ion changes from -5 to 0.
   3.   ?    The iodate ion acts as an oxidising agent.
   4.   ?    The oxidation number of hydrogen changes from + 1 to 0.

3. In which one of the following reactions is the acid acting as an oxidant?
   

   1.   ?     ZnO    +   2HNO₃   =   Zn(NO₃)₂    +   H₂O
   2.   ?    4HClO₄   +   P₄O₁₀   =   2Cl₂O₇   +   4HPO₃
   3.   ?     Cu   + 2H₂SO₄   =   CuSO₄   +  2H₂O   +   SO₂
   4.   ?     KBr   +   H₃PO₄   =   HBr   +   KH₂PO₄

4. Which one of the following equations shows hydrogen peroxide behaving as a reducing agent?
   

   1.   ?    H₂O₂   +   Ag₂O   =   2Ag   +   O₂   +   H₂O
      
      
   2.   ?    H₂O₂ + 2FeSO₄   +   H₂SO₄   =   Fe₂(SO₄)₃   +   2H₂O
   3.   ?    H₂O₂   +   Na₂SO₃   =   Na₂SO₄   +   H₂O
      
   4.   ?    H₂O₂   +   2KI   +   2HCl   =   I₂   +   2KCl +   2H₂O
      

5. Potassium permanganate has the formula KMnO₄.
   What are the oxidation numbers of potassium and manganese?
   

   potassium

   manganese

   1.   ?    

      +1

      +7

   2.   ?    

      +4

      +4

   3.   ?    

      +1

      +6

   4.   ?    

      +1

      +3

6. Which one of the following conversions is an oxidation?
   

   1.   ?    Mn²⁺ = MnCl₂
   2.   ?    MnO₄^-= MnO₄^2-
   3.   ?    Mn(OH)₂ = MnO₂
   4.   ?    Mn³⁺ = Mn₂O₃