Three thermochemical equations are given below: (i) Cgraphite+O2g →CO2(g) ; △rH =x kJ mol-1(ii) Cgraphite+12O2g →CO(g) ; △rH - Chemistry - Thermodynamics and Thermochemistry

Question

Three thermochemical equations are given below:
( i )   C g r a p h i t e + O 2 g   → C O 2 ( g )
  ;   △ r H ° = x   k J   m o l - 1 (
i i )     C g r a p h i t e + 1 2 O 2 g   → C
O ( g )   ;   △ r H ° = y   k J   m o
l - 1   ( i i i )     C O ( g ) + O 2 g  
→ C O 2 ( g )   ;   △ r H ° = z   k
J   m o l - 1
Based on the above equations, find out which of the relationship
given below is correct:
(1) x = y - z
â€‹(2) z = x + y

Rahul Yogi · Accepted Answer

Dear student,

In your question 3rd reaction is not balanced
The correct reaction is,

CO(g) + 12O2(g) →CO2(g)
Adding the reaction 2 and reaction reaction 3,
we get 1st reaction,

C + 12O2 + CO + 12O2 →CO + CO2C +O2→CO2      ∆H = y+z

Hence X=Y+Z

Hope this helps,
Regards