Chemistry: Thermodynamics

State the First Law of Thermodynamics in the context of internal energy change.

The change in internal energy (ΔU) of a system is equal to the heat (q) added to the system plus the work (w) done on the system: ΔU = q + w.

What is the sign of ΔH for an endothermic process, and what does it imply about heat flow?

ΔH is positive (ΔH > 0), implying that the system absorbs heat from its surroundings.

Define entropy (S) in a conceptual sense regarding the state of a system.

Entropy is a measure of the dispersal of energy or the degree of disorder and randomness within a system.

What characterizes a 'state function' in thermodynamics?

A state function is a property whose value depends only on the current state of the system, not on the path taken to reach that state.

What does the Third Law of Thermodynamics state regarding a perfect crystal?

The entropy of a perfect crystalline substance is zero at absolute zero (0 Kelvin).

In thermodynamics, how is the 'universe' defined?

The universe is defined as the sum of the system (the specific part being studied) and the surroundings (everything else).

Provide the Gibbs Free Energy equation and identify all variables.

ΔG = ΔH - TΔS, where G is Gibbs free energy, H is enthalpy, T is absolute temperature in Kelvin, and S is entropy.

What is the criterion for a process to be spontaneous at constant temperature and pressure in terms of ΔG?

A process is spontaneous if the change in Gibbs Free Energy is negative (ΔG < 0).

Explain Hess's Law of constant heat summation.

Hess's Law states that the total enthalpy change for a reaction is the same regardless of whether the reaction occurs in one step or several steps.

Write the formula used in calorimetry to calculate heat (q) based on temperature change.

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