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
The standard enthalpy change of the reaction can be calculated by using the formula:
ΔHcӨ(reaction) = ΣΔHcӨ(products) - ΣΔHcӨ(reactants)
ΔHcӨ(reaction) = [-890 kJ/mol] - [(1 x -394 kJ/mol) + (2 x -286 kJ/mol)]
ΔHcӨ(reaction) = -890 kJ/mol + 676 kJ/mol
ΔHcӨ(reaction) = -214 kJ/mol
Therefore, the standard enthalpy change of the reaction C(s) + 2H2(g) ⇢ CH4(g) is -214 kJ/mol.
To calculate the standard enthalpy change of the reaction C (s) + 2H2 (g) ⇢ CH4 (g), we can use the standard enthalpy changes of combustion for each substance involved.
The given values are:
C (s) = -394 kJ/mol
H2 (g) = -286 kJ/mol
CH4 (g) = -890 kJ/mol
First, let's calculate the standard enthalpy change for the reaction:
ΔH = Σ ΔHc (products) - Σ ΔHc (reactants)
For the products:
CH4 (g) has a coefficient of 1 in the balanced equation, so ΔHc (CH4) = -890 kJ/mol.
For the reactants:
C (s) has a coefficient of 1 in the balanced equation, so ΔHc (C) = -394 kJ/mol.
H2 (g) has a coefficient of 2 in the balanced equation, so ΔHc (H2) = 2 * -286 kJ/mol = -572 kJ/mol.
Now let's substitute these values into the equation:
ΔH = ΔHc (CH4) - ΔHc (C) - ΔHc (H2)
ΔH = -890 kJ/mol - (-394 kJ/mol) - (-572 kJ/mol)
ΔH = -890 kJ/mol + 394 kJ/mol + 572 kJ/mol
ΔH = 76 kJ/mol
Therefore, the standard enthalpy change of the reaction C (s) + 2H2 (g) ⇢ CH4 (g) is 76 kJ/mol.