Question

20. The following two reactions are known :
Fe2O3(s) + 3CO(g) → 2Fe(s) + 3C02(9) ;
AH = -26.8 kJ
FeO(s) + CO(g) → Fe(s) + CO2(g);AH = -16.5 kJ
The value of AH for the following reaction
Fe,O3(s) + CO(g) → 2FeO(s) + CO2(g) is
[AIPMT (Mains)-2010]
(1) +10.3 kJ
(2) 43.3 kJ
131 -10.3 kJ
(4) +6.2 kJ​

Answer 1

Answer:(4) +6.2kJ

Explanation:equation(i)-2*(eqii)

-26.8-2*(-16.5)

=6.2kJ

Answer 2

Answer:

(4) +6.2 kJ​

Explanation:

Equation 1:

$Fe_2O_3 (s)+3CO(g)>2Fe(s)+3CO_2 (9)\\\\\Delta H = -26.8 kJ$

Equation 2:

$FeO(s)+CO(g)>Fe(s)+CO_2 (g)\\\\\Delta H = -16.5 kJ$

$Fe_2O_3 (s)+CO(g)\Rightarrow2FeO(s)+CO_2(g)\\\\\Delta H=?$

(Target Equation)

Using Hess’s law we solve this,  

Equation 1 remains as it is equation 2 is reversed and multiplied by 2

(So -16.5 changes to +16.5 and it is multiplied by 2 to get 33KJ )

Both the equations are added after manipulation to arrive at the target equation  

$Fe_2 O_3(s)+3CO(g)>2Fe(s)+3CO_2(g)\\\\\Delta H_1  = -26.8 kJ\\\\2Fe(s)+2CO_2 (g)>2FeO(s)+2CO(g)\\\\\Delta H_2=+33kJ$

Upon adding we get the target equation

2Fe ,2CO and 2CO2 gets cancelled out

$Fe_2 O_3 (s)+CO(g)\Rightarrow2FeO(s)+CO_2(g)\\\\\Delta H=(-26.8+33)KJ= +6.2KJ$ (Answer)