Carbon disulfide is a colorless liquid. When pure, it is nearly odorless, but the commercial product smells vile. Carbon disulfide is used in the manufacture of rayon and cellophane. The liquid burns as follows.
CS2(l) + 3 O2(g) → CO2(g) + 2 SO2(g)
Calculate the standard enthalpy change for this reaction using standard enthalpies of formation.
To calculate the standard enthalpy change for a reaction using standard enthalpies of formation, you need to know the standard enthalpy of formation for each compound involved in the reaction. The standard enthalpy of formation (ΔHf) is the change in enthalpy when one mole of a compound is formed from its constituent elements, all in their standard states.
Here are the standard enthalpies of formation for the compounds involved in the reaction:
ΔHf(CS2) = +89.4 kJ/mol
ΔHf(CO2) = -393.5 kJ/mol
ΔHf(SO2) = -296.8 kJ/mol
ΔHf(O2) = 0 kJ/mol
The balanced chemical equation for the reaction is:
CS2(l) + 3 O2(g) → CO2(g) + 2 SO2(g)
To calculate the standard enthalpy change (ΔH) for this reaction, you can use the following equation:
ΔH = ΣΔHf(products) - ΣΔHf(reactants)
Now, substitute the values of the standard enthalpies of formation into the equation to calculate the standard enthalpy change for the reaction:
ΔH = [ΔHf(CO2) + 2ΔHf(SO2)] - [ΔHf(CS2) + 3ΔHf(O2)]
= [-393.5 kJ/mol + 2(-296.8 kJ/mol)] - [89.4 kJ/mol + 3(0 kJ/mol)]
= -393.5 kJ/mol + (-593.6 kJ/mol) - 89.4 kJ/mol
= -1076.5 kJ/mol
Therefore, the standard enthalpy change for this reaction using standard enthalpies of formation is -1076.5 kJ/mol. The negative sign indicates that the reaction is exothermic, meaning it releases heat.