What is ΔH∘rxn for the following chemical reaction?
CS2(g)+2H2O(l)→CO2(g)+2H2S(g)
You can use the following table of standard heats of formation
(ΔH∘f) to calculate the enthalpy of the given
reaction.
| Element/ Compound | Standard Heat of Formation (kJ/mol) | Element/ Compound | Standard Heat of Formation (kJ/mol) |
| H(g) | 218 | N(g) | 473 |
| H2(g) | 0 | O2(g) | 0 |
| H2O(l) | −285.8 | O(g) | 249 |
| CS2(g) | 116.7 | H2S(g) | −20.60kJ |
| C(g) | 71 | CO2(g) | −393.5kJ |
| C(s) | 0 | HNO3(aq) | −206.6 |
Express the standard enthalpy of reaction to three significant
figures and include the appropriate units.
Answer
The balanced equati on specified is, CS2 (g)+2H(CO2 (g)+2HS(g) The enthalpy of form ati on at 25°C, that is, standard enthalpy of formation [AH,°), of each component specified in the table is ΔΗ ,%(s)-116.7 kJ/mol (ΔΙ,еђна')--20.6 kJ/mol, (AH,°) o (,) Since, the heat of reaction (Hpn) is --393.5kJ/mol, and AH, o ) - 285.8kJ/mol H^o (?) og) reacthrts Here, subscripts i and j indi cates component, m, is the moles of the producti, and n, is the moles of reactantj Re-write the above equation for the present reacti on as, Observe the reaction, which is clear that m 2mol, ns()mol CO2(g) Substitute the corresponding numerical values to the variables in the above equati on АНо,-(1 mol x-393.5 kJ/mol + 2 mol x-20.6 kJ/mol)- 1 molx116.7 kJ/mol +2molx-285.8 kJ/mol - 20.2kJ Here, the value of Ayon is calculated for 1 mol of CS2 reaction with stoichiometric moles of H2O Symbolically, s20.2kI/mol of CS2 reacted