Examples of isolated system in the following topics:
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- The law of conservation of mass states that mass in an isolated system is neither created nor destroyed.
- This law states that, despite chemical reactions or physical transformations, mass is conserved -- that is, it cannot be created or destroyed -- within an isolated system.
- This law was later amended by Einstein in the law of conservation of mass-energy, which describes the fact that the total mass and energy in a system remain constant.
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- For isolated systems, entropy never decreases.
- Increases in entropy correspond to irreversible changes in a system.
- The entropy of a system is defined only if it is in thermodynamic equilibrium.
- In an isolated system such as the room and ice water taken together, the dispersal of energy from warmer to cooler always results in a net increase in entropy.
- The second law of thermodynamics shows that in an isolated system internal portions at different temperatures will tend to adjust to a single uniform temperature and thus produce equilibrium.
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- 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.
- The second law of thermodynamics says that the entropy of any isolated system always increases.
- Isolated systems spontaneously evolve towards thermal equilibrium—the state of maximum entropy of the system.
- More simply put: the entropy of the universe (the ultimate isolated system) only increases and never decreases.
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- A thermodynamic system can be any physical system with a well-defined volume in space.
- 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.
- Because the internal energy encompasses only the energy contained within a thermodynamic system, the internal energy of isolated systems cannot change.
- However, in open systems, the pressure of the system and the surroundings has stayed constant.
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- Energy can be shared between microstates of a system.
- With more available microstates, the entropy of a system increases.
- In classical thermodynamics, the second law of thermodynamics states that the entropy of an isolated system always increases or remains constant.
- These processes reduce the state of order of the initial systems.
- With more available microstates, the entropy of a system increases.
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- Conjugated ring systems having 4n π-electrons (e.g. 4, 8, 12 etc. electrons) not only fail to show any aromatic properties, but appear to be less stable and more reactive than expected.
- Examples of 8 and 12-π-electron systems are shown below, together with a similar 10 π-electron aromatic compound.
- Thus, all attempts to isolate 1,3-cyclobutadiene have yielded its dimer, or products from reactions with other compounds introduced into the reaction system.
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- If substituent Y is not a hydrogen, an alkyl group or an aryl group, there is a good chance the compound will be unstable (not isolable), and will decompose in the manner shown.
- Likewise, α-haloalcohols (Y = Cl, Br & I) cannot be isolated, since they immediately decompose with the loss of HY.
- In the LiAlH4 reduction, the resulting alkoxide salts are insoluble and need to be hydrolyzed (with care) before the alcohol product can be isolated.
- In the borohydride reduction the hydroxylic solvent system achieves this hydrolysis automatically.
- Carbonyl groups and conjugated π-electron systems are reduced by metals such as Li, Na and K, usually in liquid ammonia solution.
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- This can be convincingly demonstrated if an intermediate species can be isolated and shown to proceed to the same products under the reaction conditions.
- Some intermediates are stable compounds in their own right; however, some are so reactive that isolation is not possible.
- The potential energy of a reacting system changes as the reaction progresses.The overall change may be exothermic ( energy is released ) or endothermic ( energy must be added ), and there is usually an activation energy requirement as well.
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- In the IUPAC system of nomenclature, functional groups are normally designated in one of two ways.
- This system names amine functions as substituents on the largest alkyl group.
- Since these names are not based on a rational system, it is necessary to memorize them.
- In quinine this nitrogen is restricted to one configuration by the bridged ring system.
- It has in fact been resolved, and pure enantiomers isolated.
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- The formation of transition metal complexes with alkenes has been convincingly demonstrated by the isolation of stable platinum complexes such as Zeise's salt, K[PtCl3(C2H4)].H2O, and ethylenebis(triphenylphosphine)platinum, [(C6H5)3P]2Pt(H2C=CH2).
- This reagent must be freshly generated in the reaction system, usually by oxidation of hydrazine, and the strongly exothermic reaction is favored by the elimination of nitrogen gas (a very stable compound).