Examples of state function in the following topics:
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- In classical thermodynamics the entropy is interpreted as a state function of a thermodynamic system.
- A state function is a property depending only on the current state of the system, independent of how that state came to be achieved.
- 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).
- Thus, when the "universe" of the room and ice water system has reached a temperature equilibrium, the entropy change from the initial state is at a maximum.
- Physical chemist Peter Atkins, for example, who previously wrote of dispersal leading to a disordered state, now writes that "spontaneous changes are always accompanied by a dispersal of energy".
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- The most common oxidation states of the metal manganese are +2, +3, +4, +6, and +7; the +2 oxidation state is the most stable.
- The most common oxidation states of manganese are 2+, 3+, 4+, 6+, and 7+.
- Compounds with oxidation states 5+ (blue) and 6+ (green) are strong oxidizing agents.
- The 2+ oxidation state is the state used in living organisms for essential functions; other states are toxic for the human body.
- Permanganate (7+ oxidation state) compounds are purple and can give glass a violet color.
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- Although nitriles do not have a carbonyl group, they are included here because the functional carbon atoms all have the same oxidation state.
- Functional groups of this kind are found in many kinds of natural products.
- Some examples are shown below with the functional group colored red.
- Most of the functions are amides or esters, cantharidin being a rare example of a natural anhydride.
- Penicillin G has two amide functions, one of which is a β-lactam.
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- The Pauli exclusion principle states that no two fermions can have identical wavefunctions.
- The Pauli exclusion principle, formulated by Austrian physicist Wolfgang Pauli in 1925, states that no two fermions of the same kind may simultaneously occupy the same quantum state.
- More technically, it states that the total wave function for two identical fermions is antisymmetric with respect to exchange of the particles.
- In contrast, particles with integer spin (bosons) have symmetric wave functions; unlike fermions, bosons may share the same quantum states.
- As spin is part of the quantum state of the electron, the two electrons are in different quantum states and do not violate the Pauli exclusion principle.
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- 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.
- This statement holds true if the perfect crystal has only one state with minimum energy.
- An example of a system which does not have a unique ground state is one containing half-integer spins, for which there are two degenerate ground states.
- The entropy (S) of a substance (compound or element) as a function of temperature (T).
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- In this section we shall focus chiefly on the nature and behavior of the electronic excited states formed when a photon is absorbed by a chromophoric functional group.
- Both the ground (lowest energy electronic state) and excited states are shown as energy profiles populated by vibrational energy states (green lines) as well as rotational states (not shown).
- Overall bonding in an excited state is usually lower than in the ground state.
- The excited state may return to the ground state by emitting a photon (light blue line).
- Each electronic state will have a group of vibrational (and rotational) states, depicted by light blue lines above each state marker.
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- A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound.
- Because of this, the discussion of organic reactions is often organized according to functional groups.
- The following table summarizes the general chemical behavior of the common functional groups.
- For reference, the alkanes provide a background of behavior in the absence of more localized functional groups.
- For example, addition reactions to C=C are significantly different from additions to C=O, and substitution reactions of C-X proceed in very different ways, depending on the hybridization state of carbon.
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- For example, if a crowd is leaving a theater through a single exit door, the time it takes to empty the building is a function of the number of people who can move through the door per second.
- A mechanism in which two reacting species combine in the transition state of the rate-determining step is called bimolecular.
- If a single species makes up the transition state, the reaction would be called unimolecular.
- The relatively improbable case of three independent species coming together in the transition state would be called termolecular.
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- Functional groups are atoms or small groups of atoms (two to four) that exhibit a characteristic reactivity when treated with certain reagents.
- A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound.
- Because of their importance in understanding organic chemistry, functional groups have characteristic names that often carry over in the naming of individual compounds incorporating specific groups.
- In the following table the atoms of each functional group are colored red and the characteristic IUPAC nomenclature suffix that denotes some (but not all) functional groups is also colored.
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- Functional groups also play an important part in organic compound nomenclature; combining the names of the functional groups with the names of the parent alkanes provides a way to distinguish compounds.
- Functionalization refers to the addition of functional groups to a compound by chemical synthesis.
- In materials science, functionalization is employed to achieve desired surface properties; functional groups can also be used to covalently link functional molecules to the surfaces of chemical devices.
- Alcohols are a common functional group (-OH).
- Define the term "functional group" as it applies to organic molecules