Question

1.  
   1. Give the name of the reagent which when reacted with concentrated hydrochloric acid produce chlorine gas.  
   2. A student out to prepare iron III chloride using the apparatus shown in the diagram below. 
              
      1. Explain why:
         1. It is necessary to pass chlorine gas through the apparatus before heating begins. 
         2. Calcium oxide would be preferred to calcium chloride in the guard tube. 
      2. What property of iron (III) chloride makes it possible to be collected as shown in the diagram?  
      3. Write an equation form one chemical reaction that took place in the guard tube 
      4. The total mass of iron (III) chloride formed was found to be 0.5g.Calculate the volume of chlorine gas the reacted with iron.(Fe - = 56.0, C1 = 35.5 and Molar gas volume at 298K is 24,000cm³       
2.  
   1. Below is a graph that was obtained when different concentrations of hydrochloric acid was reacted with equal amount of calcium carbonate.
      
      The concentrations of hydrochloric acid were 0.8m, 0.5m and 0.1m. The calcium carbonate was in powder form. Match the graphs with concentrations.
      Graph I    
      Graph II      
   2. A state of equilibrium between dichromate (VI) and chromate ions is established as shown in the equation below.
      Cr₂O₇ (aq) + 20H⁻(aq)  2CrO₄(aq)+ H₂O(l)
         Orange                                 Yellow
      State and explain observation made when a few pellets of potassium hydroxide are added to the equilibrium mixture.  

Answer 1

1.  
   1. Lead(IV)Oxide/ Manganese(IV)Oxide/Potassium Manganate(IV)
   2.  
      1.  
         1. To prevent iron from being oxidized
         2. It also absorbs Cl₂, preventing it from escaping to the atmosphere.
      2. It sublimes when heated
      3. Cl₂(g) +CaO(s) → CaOCl₂(s) 
      4. (Fe - = 56.0, C1 = 35.5 and Molar gas volume at 298K is 24,000cm³       
         2Fe(s) + 3Cl2(g) → 2FeCl₃(s)
         Moles of FeCl₃ = ^0.5/_162.5
                              =0.00308moles
         Mole ratio 
         FeCl₃: Cl₂  
               2:3
         0.00308  ?
         0.00308׳/₂
         0.00462 × 24000 
            =110.88cm³ 
2.  
   1. Graph I   0.8   
      Graph II  0.5  
   2. Mixture becomes yellow
      KOH increases concentration of OH⁻ hence forward reaction is favoured