Answer to Question #193783 in General Chemistry for Kristine Olar

Question

Carbon tetrachloride can be formed by reacting chlorine with methane, calculate the enthalpy of reaction.

CH4+2Cl2-->CCl4+2H2

Answer 1

To find the enthalpy of the reaction, the values of standard enthalpies of formation of all participating compounds should be given. They are not provided here, but can be found in numerous open sources. Also, since the phases are not mentioned, we assume that the compounds are in their standard state (CCl₄ liquid, and the rest - gases).

$\Delta{H_f}(CCl_4(l))=-128.4kJ/mol$

$\Delta{H_f}(CH_4(g))=-74.8kJ/mol$

$\Delta{H_f}$ for Cl₂ and H₂ are in fact zero (for all compounds made of one type of atoms).

$\Delta{H_{reaction}}=\sum{\Delta{H_f(products)-\sum{\Delta{H_f}(reactants)}}}=\Delta{H_f(CCl_4)-\Delta{H_f}(CH_4)}=-128.4-(-74.8)=-53.6kJ/mol$

Answer: -53.6 kJ/mol