Thermodynamics Lecture Notes

These flashcards cover key concepts in thermodynamics, focusing on energy changes, calorimetry, enthalpy, and experimental procedures.

What is the equation for the total change in a system's internal energy?

ΔE = q + w, where ΔE is the change in internal energy, q is heat, and w is work.

How is the sign of energy change defined in a thermodynamic system?

Energy transferred into the system is positive, while energy transferred out of the system is negative.

When there is only heat transfer in a system and no work, how is the equation simplified?

ΔE = q, since w = 0.

What does a positive value of q indicate?

The system is gaining heat.

What does a negative value of q indicate?

The system is losing heat.

What is enthalpy (H) in thermodynamics?

A thermodynamic variable used for reactions at constant pressure, where ΔH = ΔE + PΔV.

In calorimetry, how is the quantity of heat (q) related to specific heat capacity?

q = m × c × ΔT, where m is mass, c is specific heat capacity, and ΔT is the change in temperature.

What assumption is made with a coffee-cup calorimeter?

No heat escapes the calorimeter.

In calorimetry, what happens to the heat released by a chemical reaction?

It is absorbed by the solution.

What is the specific heat capacity (c) defined as?

The quantity of heat required to change the temperature of 1 gram of a substance by 1 K.

What does Hess's Law state?

The enthalpy change for an overall reaction is the sum of the enthalpy changes for its individual steps.

What is the standard state for metals?

The standard state for metals is solid.

How do you find the enthalpy change (ΔH) for a reaction using Hess's Law?

ΔH° rxn = ΣmΔH° f(products) − ΣnΔH° f(reactants).

What do you understand by the concept of limiting reactant?

The reactant that is completely consumed in a chemical reaction, limiting the amount of product formed.

What is the relationship between qsoln and qrxn?

qsoln = -qrxn in a coffee-cup calorimeter.

What is the function of a calorimeter in thermodynamics experiments?

To measure heat transfer during chemical reactions or physical changes.

What materials are typically involved in the calibration and experiments using a calorimeter?

DI water, strong acids, strong bases, and specific metal samples for specific heat calculations.