Question

The diagram below shows a set-up that can be used to obtain nitrogen gas in an experiment.

1.  
   1. Name liquid L 
   2. What observation would be made in tube K after heating for some time? 
   3. Write an equation for the reaction that took place in tube K. 
   4. If 320cm³ of ammonia gas reacted completely with the copper?
      Calculate:
      1. Volume of nitrogen gas produced. (1mk)
      2. the mass of copper oxide that reacted (3mks)
         (Cu = 63.5, O=16.O, one mole of gas occupies 24 litres at room temperature and pressure)
   5. At the end of experiment the PH of the water in the beaker was found to be about 2. Explain.

Answer 1

1. Liquid L- water 
2. Black Copper (II) Oxide changes to brown Copper metal 
3. 2CuO_(s) + 2NH_3(g) → 3Cu_(s) + 3H₂O_(l) +N_2(g) 
4.  
   • 2×24litres of NH₃ produce 24litres N₂  
     48000cm³ NH₃ produce 24000cm³ N₂ 
     ∴ 320cm³ NH₃ produce   320  × 24000cm³ N₂
                                       48000
                           =160cm³ N₂  
   • 2 Moles NH₃ produce 3 moles CuO  
     48000cm³ NH₃ produce 238.5g CuO
     ∴ 320cm³ NH₃ produce   320  × 238.5g CuO   
                                       48000
                                     =1.59g  
5. Ammonia dissolved in the water to form ammonia solution which is a weak base.