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A and B can react to form C and D or, in the reverse reaction, C and D can react to form A and B. This is distinct from a reversible process in thermodynamics. Weak acids and bases undergo reversible reactions. For example, carbonic acid: H 2 CO 3 (l) + H 2 O (l) ⇌ HCO 3 − (aq) + H 3 O + (aq).
[a] While processes in isolated systems are never reversible, [3] cyclical processes can be reversible or irreversible. [4] Reversible processes are hypothetical or idealized but central to the second law of thermodynamics. [3] Melting or freezing of ice in water is an example of a realistic process that is nearly reversible.
The second law of thermodynamics can be used to determine whether a hypothetical process is reversible or not. Intuitively, a process is reversible if there is no dissipation. For example, Joule expansion is irreversible because initially the system is not uniform. Initially, there is part of the system with gas in it, and part of the system ...
Equality of forward and backward reaction rates, however, is a necessary condition for chemical equilibrium, though it is not sufficient to explain why equilibrium occurs. Despite the limitations of this derivation, the equilibrium constant for a reaction is indeed a constant, independent of the activities of the various species involved ...
where k f is the rate constant for the forward reaction and k b is the rate constant for the backward reaction and the square brackets, […], denote concentration. If only A is present at the beginning, time t = 0 , with a concentration [A] 0 , the sum of the two concentrations, [A] t and [B] t , at time t , will be equal to [A] 0 .
Reversible Michaelis–Menten kinetics, using the reversible form of the Michaelis–Menten equation, is therefore important when developing computer models of cellular processes involving enzymes. In enzyme kinetics, the Michaelis–Menten kinetics kinetic rate law that describes the conversion of one substrate to one product, is often ...
In physics, Loschmidt's paradox (named for J.J. Loschmidt), also known as the reversibility paradox, irreversibility paradox, or Umkehreinwand (from German 'reversal objection'), [1] is the objection that it should not be possible to deduce an irreversible process from time-symmetric dynamics.
In 1884, Jacobus van 't Hoff proposed the Van 't Hoff equation describing the temperature dependence of the equilibrium constant for a reversible reaction: = where ΔU is the change in internal energy, K is the equilibrium constant of the reaction, R is the universal gas constant, and T is thermodynamic temperature.