question_answer 45)

  On the basis of thermo chemical equations (i), (ii) and (iii),find out which of the algebraic relationships given in options (a) to (d) is correct: (i) \[C(graphite)+{{O}_{2}}(g)\to C{{O}_{2}}(g);\,\,\,{{\Delta }_{r}}H=x\,kJ\,mo{{l}^{-1}}\] (ii) \[C(graphite)+\frac{1}{2}{{O}_{2}}(g)\to CO(g);\,\,{{\Delta }_{r}}H=y\,kJ\,mo{{l}^{-1}}\] (iii) \[CO(g)+\frac{1}{2}{{O}_{2}}(g)\to C{{O}_{2}}(g);\]\[{{\Delta }_{r}}H=z\,\,kJ\,mo{{l}^{-1}}\] (a) \[z=x+y\]                      (b) \[x=y-z\]                       (c) \[x=y+z\]                      (c)\[y=2z-x\]

Answer:

  (c) (i) \[C\text{ }\left( graphite \right)\text{ }+{{O}_{2}}(g)\to C{{O}_{2}}(g);\,\,\,\,\,\Delta H=x\,kJ\,mo{{l}^{-1}}\] (ii) \[C\text{ }\left( graphite \right)+\frac{1}{2}{{O}_{2}}(g)\to CO(g);\,\,\,\Delta H=y\,kJ\,mo{{l}^{-1}}\] (iii) \[CO(g)+\frac{1}{2}{{O}_{2}}(g)\to C{{O}_{2}}(g);\,\,\,\,\Delta H=z\,kJ\,mo{{l}^{-1}}\] Equation (i) can be obtained by adding (ii) and (iii) hence \[x=y+z.\]