what is the difference between these two equation:
delta G= delta H-T(delta S)
and deltaG(knot)=delta H(knot)-T(delta S knot)
Which G do i use to tell whether the reaction is spontaneous
The first delta G is for a general reaction at the specified conditions. The delta Go is a "standard delta G as 25 C" when using delta Hformation at 25 and delta Sformation at 25C.
(I assume knot means naught).
Delta G is the one to use for spontaneity but remember delta G is zero when the system is at equilibrium.
The two equations you mentioned relate to Gibbs free energy (G) and are used to determine the spontaneity of a reaction.
The first equation, delta G = delta H - T(delta S), is the general equation for calculating the change in Gibbs free energy (delta G) for a reaction at any temperature (T). It takes into account the change in enthalpy (delta H) and the change in entropy (delta S) of the system.
The second equation, delta G(knot) = delta H(knot) - T(delta S knot), is a specific form of the first equation, which applies when the reaction is at standard conditions. The superscript "knot" (°) denotes standard conditions, where the pressure is 1 bar and the temperature is 298 K.
To determine whether a reaction is spontaneous, you need to compare the value of delta G (or delta G(knot)) to 0. If delta G < 0 (or delta G(knot) < 0), the reaction is spontaneous and will proceed in the forward direction. If delta G > 0 (or delta G(knot) > 0), the reaction is non-spontaneous and will not proceed in the forward direction without external influence. If delta G = 0 (or delta G(knot) = 0), the system is at equilibrium, meaning the reaction can occur in both the forward and reverse directions at equal rates.
I would like to note that the actual calculation of delta G (or delta G(knot)) requires knowing the values of delta H (enthalpy change) and delta S (entropy change). These values can be found from experimental data or calculated using various thermodynamic relationships.