Question

As an approximation, we can assume that proteins exist either in the native state or in the denatured state. The standard molar enthalpy and entropy of the denaturation for a certain protein are 542 kJ.mol^-1 and 1.72 kJ.K^-1.mol^-1, respectively. Comment on the signs and magnitudes of these quantities, and calculate the temperature at which the denaturation becomes spontaneous.

Answer 1

Enthalpy H = 542 kJ.mol^-1

Entropy S = 1.72 kJ.K^-1.mol^-1

if it becomes spontaneous Gibbs free energy change is negative ( G < 0 )

G = H - T S

G < 0 for spontaneous

H < T S

H / S < T

542 / 1.72 < T

315.1 < T

T > 315.1 K

temperature = 315 K

if G negative ( G = -ve = < 0) that is spontaneous. to get G < 0 , the signs for H , S are

if H = -ve , S = + ve   spontaneous

if H = -ve , S = -ve , spontaneous at low temperatures, and non - spontaneous at high temperatures.