Stock system

Examples of Stock system in the following topics:

• Naming Ionic Compounds

  • CaBr2 can be named using either the Stock method or the older, classic way of naming.
  • This system is still used, although it has been officially supplanted by the more precise, if slightly cumbersome, Stock system.
  • In both systems, the name of the anion ends in -ide.

• Comparison of Enthalpy to Internal Energy

  • A thermodynamic system can be any physical system with a well-defined volume in space.
  • The outer edge of the system is referred to as its boundary, which often separates the system from the surroundings.
  • Hence, -q means the system loses heat, while +q means a system gains heat.
  • Similarly, +w means work is done on the system, while -w means work is done by the system.
  • However, in open systems, the pressure of the system and the surroundings has stayed constant.

• Dilutions of Solutions

  • Diluting solutions is a necessary process in the laboratory, as stock solutions are often purchased and stored in very concentrated forms.
  • Serial dilutions involve diluting a stock or standard solution multiple times in a row.

• Changes in Energy

  • For isolated systems, entropy never decreases.
  • Increases in entropy correspond to irreversible changes in a system.
  • This is because some energy is expended as heat, limiting the amount of work a system can do.
  • The state function has the important property that in any process where the system gives up energy ΔE, and its entropy falls by ΔS, a quantity at least TR ΔS of that energy must be given up to the system's surroundings as unusable heat (TR is the temperature of the system's external surroundings).
  • The entropy of a system is defined only if it is in thermodynamic equilibrium.

• The Three Laws of Thermodynamics

  • Everything that is not a part of the system constitutes its surroundings.
  • The system and surroundings are separated by a boundary.
  • A closed system may still exchange energy with the surroundings unless the system is an isolated one, in which case neither matter nor energy can pass across the boundary.
  • Conversely, heat flow out of the system or work done by the system (on the surroundings) will be at the expense of the internal energy, and q and w will therefore be negative.
  • Isolated systems spontaneously evolve towards thermal equilibrium—the state of maximum entropy of the system.

• Microstates and Entropy

  • Energy can be shared between microstates of a system.
  • With more available microstates, the entropy of a system increases.
  • These processes reduce the state of order of the initial systems.
  • With more available microstates, the entropy of a system increases.
  • The more such microstates, the greater is the probability of the system being in the corresponding macrostate.

• Free Energy and Work

  • The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system.
  • Gibbs energy is the maximum useful work that a system can do on its surroundings when the process occurring within the system is reversible at constant temperature and pressure.
  • The work is done at the expense of the system's internal energy.
  • ΔG is the maximum amount of energy which can be "freed" from the system to perform useful work.
  • "Useful" in this case, refers to the work not associated with the expansion of the system.

• The Third Law of Thermodynamics and Absolute Energy

  • The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches zero.
  • At zero temperature the system must be in a state with the minimum thermal energy.
  • A more general form of the third law applies to systems such as glasses that may have more than one minimum energy state: the entropy of a system approaches a constant value as the temperature approaches zero.
  • The constant value (not necessarily zero) is called the residual entropy of the system.
  • For such systems, the entropy at zero temperature is at least ln(2)kB, which is negligible on a macroscopic scale.

• Pressure and Free Energy

  • Gibbs free energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.
  • The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system.
  • When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force.
  • Gibbs energy (also referred to as ∆G) is also the chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature.

• Standard Units (SI Units)

  • The International System of Units (abbreviated SI) is the metric system used in science, industry, and medicine.
  • The International System of Units (abbreviated SI, from the French Système international d'unités) is the metric system used in science, industry, and medicine.
  • The imperial system is used for "everyday" measurements in a few places, such as the United States.
  • The use of the SI system provides all scientists and engineers with a common language of measurement.
  • Causey teaches scientific units of the SI system, the metric system, and the CGS system.