Select the appropriate mole ratio expression needed to find the concentration of the unknown solution for each of these titration problems.

1. 20.0 mL of 0.114 mol L^-1 oxalic acid reacted with 23.7 mL of MnO₄^- solution.
   5C₂O₄^2- + 2MnO₄^- + 16H⁺ 10CO₂ + 2Mn²⁺ + 8H₂O

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

2. 25.0 mL of diluted hydrogen peroxide solution reacts with 31.1 mL of 0.0184 mol L^-1 MnO₄^- solution.
   2MnO₄^- + 5H₂O₂ + 6H⁺ 2Mn²⁺ + 5O₂ + 8H₂O

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

3. 13.6 mL of MnO₄^- solution reacts with 25.0 mL of 0.0848 mol L^-1 Fe²⁺ solution.
   MnO₄^- + 5Fe²⁺ + 8H⁺ Mn²⁺ + 5Fe³⁺ + 4H₂O

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

4. 12.3 mL of 0.00400 mol L^-1 Cr₂O₇^2- reacts with 10.0 mL of ethanol solution.
   3CH₃CH₂OH + 2Cr₂O₇^2- + 16H⁺ 3CH₃COOH + 4Cr³⁺ + 11H₂O

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

5. 20.0 mL of diluted household bleach oxidised KI solution to I₂. The iodine was titrated against 0.104 mol L^-1 thiosulfate solution and required 32.5 mL.
   OCl^- + 2H⁺ + 2I^- I₂ + Cl^- + H₂O
   I₂ + 2S₂O₃^2- 2I^- + S₄O₆^2-

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

6. 20.0 mL of a 0.0175 mol L^-1 KBrO₃ solution is reacted with KI and the iodine liberated reacted with 28.9 mL of thiosulfate solution.
   BrO₃^- + 6I^- + 6H⁺ Br^- + 3I₂ + 3H₂O
   I₂ + 2S₂O₃^2- 2I^- + S₄O₆^2-

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?    

7. 10.0 mL of a Cu²⁺ solution was reacted with KI and the iodine liberated titrated against 0.025 mol L^-1 thiosulfate solution. 26.4 mL of thiosulfate were required.
   2Cu²⁺ + 4I^- 2CuI + I₂
   I₂ + 2S₂O₃^2- 2I^- + S₄O₆^2-

   1.   ?    
   2.   ?    
   3.   ?    
   4.   ?