The table below shows some values for standard enthalpy changes of combustion. Use these values in the table below to calculate the standard enthalpy change of the reaction
C (s) + 2H2 (g) ⇢CH4 (g)
Substance
incrementHc Ө / kJ/mol
C (s)
-394
H2 (g)
-286
CH4 (g)
-890
-76 kJ/mol
-604 kJ/mol
-210 kJ/mol
-318 kJ/m
ol
To calculate the standard enthalpy change of the reaction C (s) + 2H2 (g) ⇢ CH4 (g), we'll need to use the standard enthalpy changes of combustion for each species involved.
The standard enthalpy change of combustion for C (s) is -394 kJ/mol.
The standard enthalpy change of combustion for H2 (g) is -286 kJ/mol.
The standard enthalpy change of combustion for CH4 (g) is -890 kJ/mol.
Using these values, we can calculate the standard enthalpy change of the reaction by summing up the products and subtracting the sum of the reactants.
ΔH = ΣΔH(products) - ΣΔH(reactants)
For this reaction, the product is CH4 (g) and the reactants are C (s) and 2H2 (g). Substituting the values into the equation, we have:
ΔH = (-890) - ( -394 + 2*(-286) )
Simplifying the equation:
ΔH = -890 + 394 - 2*(-286)
ΔH = -890 + 394 + 572
ΔH = 76 kJ/mol
Therefore, the standard enthalpy change of the reaction C (s) + 2H2 (g) ⇢ CH4 (g) is -76 kJ/mol.