1.which of the following combinations will result in a reaction that is never spontaneous? . a) positive enthalpy change and positive entropy change. b) positive enthalpy change and negative entropy change. c) negative enthalpy change and positive entropy change. d) negative enthalpy change and negative entropy change. 2.which of the following changes will always be true for an exothermic process? . a) + delta h. b) + delta s. c) - delta h. d) - delta g

b) positive enthalpy change and negative entropy change.

c) - delta H.

Explanation:

The total energy or intrinsic energy(heat content) of a system is known as the enthalpy.

Entropy deals with the degree of randomness or disorderliness of a system.

The fraction of the total heat energy of system that does useful work is the Gibb's free energy(G).

  The standard free energy change of system is expressed as:

                   ΔG° = ΔH° - TΔS°

ΔH° is the standard enthalpy change

ΔS° is the standard entropy change

T is the temperature

The sign of ΔG° can predict whether or not a change is spontaneous or not.

if ΔG° is negative, the change is spontaneous or feasible

  ΔG° is positive then the change is non-spontaneous or non-feasible.

  ΔG° is zero, the system is in equilibrium.

From free energy change equation, we see that if ΔH° is positive and ΔS° is negative, the value of the standard free energy change is positive and the reaction is non-spontaneous.

2 . c) - delta H i.e -ΔH

An exothermic change is a change in which heat is liberated to the surroundings. In this change, the surrounding is hotter at the end of the change. ΔH is assigned a negative sign as the sum of the heat contents of the products are less than that of the heat contents of the reactants.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.