Given the enthalpy reactions below,
2 X + O2 → 2 XO ΔHrxn = -1301.8 kJ/rxn
XCO3 → XO + CO2 ΔHrxn = 169.7 kJ/rxn
What is the ΔHrxn for this reaction?
2 X + O2 + 2 CO2 → 2 XCO3
2 X + O2 + 2 CO2 → 2 XCO3
but 2X+O2>2XO -1301.8kJ
2XO+2CO2>2XCO3 -169.7*2 kJ
so heat of reaction is ..add them up, about -1640 kJ if I added them up correctly.
To find the ΔHrxn for the reaction: 2 X + O2 + 2 CO2 → 2 XCO3, you can use the Hess's Law, which states that the enthalpy change of a reaction is independent of the pathway between the initial and final states.
To apply Hess's Law, you need to manipulate the given reactions to match the desired reaction. In this case, you need to reverse the second reaction and multiply it by 2, then reverse the first reaction and multiply it by a coefficient of 2.
Here's the manipulation of the reactions:
2 (XCO3 → XO + CO2) ΔH1 = 2 * (-169.7 kJ/rxn) = -339.4 kJ
2 (2 XO → 2 X + O2) ΔH2 = 2 * (-(-1301.8 kJ/rxn)) = 2 * 1301.8 kJ = 2603.6 kJ
Now add the manipulated reactions:
2 X + O2 + 2 CO2 ΔHrxn = ΔH1 + ΔH2
= -339.4 kJ + 2603.6 kJ
= 2264.2 kJ/rxn
Therefore, the ΔHrxn for the given reaction is +2264.2 kJ/rxn.