Question

Which of the reactions are spontaneous (favorable)?

Answer 1

A spontaneous reaction proceeds without external energy input and has a negative Gibbs free energy change (∆G < 0). Exercises illustrate spontaneous processes like combustion or rusting, and determining the temperature range for spontaneity entails calculating ∆H and ∆S, then using ∆G = ∆H - T∆S.

Step-by-step explanation:

A spontaneous reaction is one that occurs naturally and proceeds without the need for continuous external energy. It is characterized by an overall decrease in Gibbs free energy (∆G < 0). In contrast, a nonspontaneous reaction requires the input of energy to proceed (∆G > 0).

According to the exercises given:

1. Spontaneous reactions such as the combustion of gasoline or iron rusting in a moist atmosphere, happen without external input, often releasing energy and resulting in an increase in entropy.
2. Nonspontaneous processes, like a ball being thrown into the air, require continuous external energy to be sustained.
3. The spontaneous deflation of a helium balloon overnight demonstrates the redistribution of matter, as helium atoms diffuse out, representing an increase in entropy as the matter disperses.

The determination of spontaneity over a temperature range involves calculating ∆H and ∆S (assuming these values are temperature independent) and then using the equation ∆G = ∆H - T∆S to find the range over which ∆G is negative.