If you need to multiply the following reaction by 2 to be an intermediate reaction in a Hess's law problem, what would be the final value for the enthalpy of reaction you use for this intermediate reaction? C2H4 + 3 O2 2 CO2 + 2 H2O, H = -1410 kJ
-2820 kj
The answers -2820 kj (APEX)
It works this way. If you multiply the equation you use the same multiplier for dH. If you reverse the equation, change the sign of dH. If you reverse the equation AND multiply it, then multiply by the same multiplier and change the sign.
To multiply the given reaction by 2, you need to double all the coefficients in the balanced equation:
2 C2H4 + 6 O2 → 4 CO2 + 4 H2O
When you multiply the coefficients, the value of ΔH for the reaction also needs to be doubled. Therefore, the final value for the enthalpy of reaction for this intermediate reaction would be:
ΔH = -1410 kJ × 2 = -2820 kJ
So, the final value for the enthalpy of reaction for this intermediate reaction would be -2820 kJ.