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.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).