Question

Thermochemistry Lab

1. Briefly explain, in terms of heat exchange, how you determined the heat capacity of the calorimeter.

2.Briefly explain, in terms of heat exchange, how you determined the heat of neutralization qreaction.

3. How does the q reaction differ from ΔH neutralization? Which value is an intensive property? Explain.

4. Do your values of ΔH for each reaction follow the expected trend?

5. Does it take more or less energy to break the weak acid bond or the weak base bond? (Compare ΔHWA,ΔHWB)? Are the reactions endothermic or exothermic? Why?

6. Discuss two sources of error.

Answer 1

3)

q is the amount of heat transfered to the system. It is one of the two means of energy transfer during most processes studied in thermodynamics. The other means of transferring energy is through work. Since these are the only means by which we can transfer energy between the system and the surroundings, we can write the change of internal energy of our thermodynamic system as:

ΔE= q + w
(note: some books denote internal energy as U)

The heat of neutralization(better known as enthalpy of neutralization) is the energy released when one equivalent of acid reacts with one one equivalent of a base (neutralization reaction) to produce salt and water as the products. It is a type of enthalpy of reaction.

Intensive properties are properties whose values do not depend on the mass or amount of material present in system i.e. the are independent of mass. While extensive properties depend on mass or the amount of material present in system

ΔH neutralization is an extensive property.

Actually, Heat, which in thermodynamics has the symbol q, is a measure of the energy lost or gained by the system and is not a as such, a property of the system. It is a function of the amount of internal energy in the system, which is a property, versus that outside of the system, as well as a bunch of other properties like temperature, pressure, volume. So perhaps it’s better to say that internal energy is an extensive property, which depends on the amount of material.