The most concentrated solution is b
        
                    
             
        
        
        
Gold is found in pure state in nature but not the iron because gold is un-reactive metal, so it does not react with other element in normal condition but iron is reactive metal so it reacts with atmospheric oxygen in presence of moist (water) to form oxide.
Explanation:
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Answer:

Explanation:
                 Ba(OH)₂ + 2HCl ⟶ BaCl₂ + H₂O
     V/mL:     249
c/mol·L⁻¹:  0.0443     0.285
1. Calculate the moles of Ba(OH)₂

2. Calculate the moles of HCl
The molar ratio is 2 mol HCl:1 mol Ba(OH)₂

3. Calculate the volume of HCl
