Question

A chemical reaction that proceeds spontaneously _____.

must run in the direction that lowers the free energy
must produce products that are more ordered than the reactant molecules
must proceed without an input of external energy
must take place in a very short amount of time

Answer 1

A chemical reaction that proceeds spontaneously must run in the direction that lowers the free energy.

Step-by-step explanation:

Spontaneity is related to the free energy (ΔG), which is related to entropy (ΔS) and enthalpy (ΔH).

ΔG = ΔH - TΔS

It is stated that a spontaneous reaction will release energy, therefore decreasinf the free energy.

This will definitely happen if the reaction is exothermic (proceeds without an imput of energy; ΔH < 0) and the products are more disordered (ΔS>0).

A reaction can be endothermic ( requires an imput of energy; ΔH > 0) if the temperature and ΔS are high enough.

Answer 2

To answer the question above, remember that the chemical reactions that proceed spontaneously need not have an external energy to drive the reaction. Therefore the answer to this item is the third choice, "must proceed without an input of external energy".