Calculate the enthalpy change for the reactionC(s) + 2 H2(g) → CH4(g) ΔH = ?Given the enthalpy values for the following reactionsCH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) ΔH = −890.4 kJC(s) + O2(g) → CO2(g) ΔH = −393.5 kJH2(g) + 1/2 O2(g) → H2O (g) ΔH = −285.8 kJ(a) −1569.7 kJ(b) +211.1 kJ(c) −1855.5 kJ(d) −74.7 kJ

Enthalpy change, denoted as ΔH, represents the heat content change of a system during a chemical reaction at constant pressure. It can be either exothermic (releasing heat, ΔH < 0) or endothermic (absorbing heat, ΔH > 0). Understanding ΔH is crucial for predicting the energy changes associated with reactions, which is essential for calculating the overall enthalpy change in a reaction pathway.

Hess's Law states that the total enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps of the reaction, regardless of the pathway taken. This principle allows chemists to calculate the enthalpy change for a reaction that may be difficult to measure directly by using known enthalpy values from related reactions. It is particularly useful in this problem to derive the enthalpy change for the formation of methane from the given reactions.

The standard enthalpy of formation is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. For the reaction in question, the standard enthalpy of formation for CH4(g) is indirectly calculated using the enthalpy values of combustion and formation of reactants and products. This concept is vital for determining the ΔH of the reaction involving carbon and hydrogen to form methane.