Input interpretation
methane ⟶ hydrogen + acetylene
Balanced equation
Balance the chemical equation algebraically: ⟶ + Add stoichiometric coefficients, c_i, to the reactants and products: c_1 ⟶ c_2 + c_3 Set the number of atoms in the reactants equal to the number of atoms in the products for C and H: C: | c_1 = 2 c_3 H: | 4 c_1 = 2 c_2 + 2 c_3 Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 3 c_3 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 ⟶ 3 +
Structures
⟶ +
Names
methane ⟶ hydrogen + acetylene
Reaction thermodynamics
Enthalpy
| methane | hydrogen | acetylene molecular enthalpy | -74.6 kJ/mol | 0 kJ/mol | 227.4 kJ/mol total enthalpy | -149.2 kJ/mol | 0 kJ/mol | 227.4 kJ/mol | H_initial = -149.2 kJ/mol | H_final = 227.4 kJ/mol | ΔH_rxn^0 | 227.4 kJ/mol - -149.2 kJ/mol = 376.6 kJ/mol (endothermic) | |
Gibbs free energy
| methane | hydrogen | acetylene molecular free energy | -51 kJ/mol | 0 kJ/mol | 209.9 kJ/mol total free energy | -102 kJ/mol | 0 kJ/mol | 209.9 kJ/mol | G_initial = -102 kJ/mol | G_final = 209.9 kJ/mol | ΔG_rxn^0 | 209.9 kJ/mol - -102 kJ/mol = 311.9 kJ/mol (endergonic) | |
Entropy
| methane | hydrogen | acetylene molecular entropy | 186 J/(mol K) | 115 J/(mol K) | 201 J/(mol K) total entropy | 372 J/(mol K) | 345 J/(mol K) | 201 J/(mol K) | S_initial = 372 J/(mol K) | S_final = 546 J/(mol K) | ΔS_rxn^0 | 546 J/(mol K) - 372 J/(mol K) = 174 J/(mol K) (endoentropic) | |
Chemical names and formulas
| methane | hydrogen | acetylene Hill formula | CH_4 | H_2 | C_2H_2 name | methane | hydrogen | acetylene IUPAC name | methane | molecular hydrogen | acetylene
Substance properties
| methane | hydrogen | acetylene molar mass | 16.04 g/mol | 2.016 g/mol | 26.038 g/mol phase | gas (at STP) | gas (at STP) | gas (at STP) melting point | -182.47 °C | -259.2 °C | -81 °C boiling point | -161.48 °C | -252.8 °C | -75 °C density | 6.67151×10^-4 g/cm^3 (at 20 °C) | 8.99×10^-5 g/cm^3 (at 0 °C) | 0.618 g/cm^3 (at -55 °C) solubility in water | soluble | | surface tension | 0.0137 N/m | | 0.01431 N/m dynamic viscosity | 1.114×10^-5 Pa s (at 25 °C) | 8.9×10^-6 Pa s (at 25 °C) | odor | odorless | odorless |
Units
