Please help!
I need to calculate the enthalpy change of the POCL3.
From what to what?
Well the question state that:
Using the molar bond enthalpies given in table 2, calculate the overall enthalpy change for reaction POCL3.
Table 2:
P-CL 326
O=O 498
P=O 544
Thanks for your help. By Lowrence.
This looks very much like the S104 TMA04 question?
To calculate the enthalpy change (∆H) of a chemical reaction, you typically need the balanced chemical equation for the reaction, as well as the known enthalpy changes of formation (∆Hf) for the reactants and products involved.
In the case of POCl3 (phosphorus oxychloride), we can use the following balanced equation to calculate the enthalpy change:
P4 + 6 O2 + 6 Cl2 → 4 POCl3
To calculate the ∆H of POCl3, we need to know the ∆Hf values for each species involved in the reaction.
Here's a step-by-step guide to determine the enthalpy change of POCl3:
1. Look up the ∆Hf values for P4 (phosphorus), O2 (oxygen), Cl2 (chlorine), and POCl3. These values are usually given in a reference table or can be found in databases.
2. Determine the stoichiometric coefficients in the balanced equation. In this case, we have 1 mol of P4, 6 mol of O2, 6 mol of Cl2, and 4 mol of POCl3.
3. Calculate the ∆H of the reaction. Multiply the stoichiometric coefficients of each reactant and product by their corresponding ∆Hf values, and then subtract the sum of the reactants' enthalpies from the sum of the products' enthalpies:
∆H = (4 ∆Hf[POCl3]) - (1 ∆Hf[P4] + 6 ∆Hf[O2] + 6 ∆Hf[Cl2])
4. Substitute the relevant ∆Hf values from the reference table or database into the equation and perform the calculation.
Keep in mind that the ∆Hf values are typically given per mole of substance under standard conditions (298 K and 1 atm pressure). If the values are given in a different unit, you may need to adjust them accordingly.
Remember to pay attention to the sign convention of enthalpy changes. A positive ∆H indicates an endothermic reaction (absorbs heat), while a negative ∆H indicates an exothermic reaction (releases heat).
By following this process, you should be able to calculate the enthalpy change of POCl3.