Enthalpy changes:
H2O2(l) ----> H2O(l) + 1/2P2(g) delta H= -94.6kJ
H2(g) + 1/2O2(g)----> H2O2 delta H= -286.0kJ
Calculate the value on delta H for the reaction:
H2(g) + H2O2(l)----> 2H2O(l)
−187.6 kJ/mol
To calculate the value of ΔH for the reaction H2(g) + H2O2(l) → 2H2O(l), we can use the given enthalpy changes for the given reactions:
1. Multiply the second reaction by 2 to balance the number of moles of H2O2 on both sides:
2H2(g) + O2(g) ----> 2H2O2 ΔH = -572.0 kJ
2. Multiply the first reaction by 2 and reverse it to match the reactants in the desired reaction:
2H2O(l) + P2(g) ----> 2H2O2(l) ΔH = 94.6 kJ
3. Add the two equations together to obtain the desired reaction:
2H2(g) + 2H2O(l) + P2(g) ----> 4H2O(l) ΔH = -477.4 kJ
Therefore, the value of ΔH for the reaction H2(g) + H2O2(l) → 2H2O(l) is -477.4 kJ.
To calculate the value of ΔH for the reaction H2(g) + H2O2(l) → 2H2O(l), we can use the concept of Hess's law.
Hess's law states that the overall enthalpy change in a reaction is equal to the sum of the enthalpy changes of the individual steps of the reaction. In other words, if we can find the enthalpy changes for the steps involved in the reaction, we can add them together to find the overall enthalpy change.
To do this, we need to manipulate the given reactions and combine them in a way that will cancel out the desired reactants and products.
1. Multiply the first equation (H2(g) + 1/2O2(g) → H2O2) by 2 to balance the number of moles of H2O2 with the desired equation:
2H2(g) + O2(g) → 2H2O2(l) ΔH = 2*(-286.0 kJ) = -572 kJ
2. Reverse the first equation to match the desired reaction:
2H2O2(l) → 2H2(g) + O2(g) ΔH = 572 kJ
3. Multiply the second equation (H2O2(l) → H2O(l) + 1/2P2(g)) by 4 to balance the number of moles of H2O2 with the desired equation:
4H2O2(l) → 4H2O(l) + 2P2(g) ΔH = 4*(-94.6 kJ) = -378.4 kJ
4. Add the equations together to obtain the desired reaction:
4H2O2(l) + 2H2(g) + O2(g) → 4H2O(l) + 2P2(g) ΔH = -378.4 kJ + 572 kJ = 193.6 kJ
Therefore, the value of ΔH for the reaction H2(g) + H2O2(l) → 2H2O(l) is 193.6 kJ.