Constants | Periodic Table Learning Goal: To understand how to use Hess\'s law t

Question

Constants | Periodic Table Learning Goal: To understand how to use Hess's law to find the enthalpy of an overall reaction The change in enthalpy, AH, is the heat absorbed or produced during any reaction at constant pressure. Hess's law states that for an overall reaction is the sum of the values for the individual reactions. For example, if we wanted to know the enthalpy change for the reaction 3Mn +302 3MnO2 we could calculate it using the enthalpy values for the following individual steps Step 1: 4AI + 3022A1203 Step 2.3Mn + 2A12033MnO2 + 4A1 Overall 3Mn + 3023MnO2 If the enthalpy change is -3352 kJ/mol for step 1 and 1792 kJ/mol for step 2, then the enthalpy change for the overall reaction is calculated as follows: H3352 + 1792 1560 kJ/mol It is also important to note that the change in enthalpy is a state function, meaning it is independent of path. In other words, the sum of the H values for any set of reactions that produce the desired product form the starting materials gives the same overall 11

Explanation / Answer

part A:

overall reaction is

C + 1/2 O2 ...........> CO

reverse the reaction 1,

we get

CO2 ..............> CO + 1/2 O2.......> (3) .........> delta H = + 283 KJ / mole.

reaction 2 add with reaction 3,

we get, C + 1/2 O2 ...........> CO

delta H = + 283 - 393 = -110 KJ/mole (answer)

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---