Q20.64 P - Chemistry: Molecular Nature Of Matter And Change

Question

(a) If K<<1 for a reaction, what do you know about the sign and magnitude of ${\mathbf{\text{ΔG}}}^{\mathbf{\text{°}}}$ ? 

(b) If ${\mathbf{\text{ΔG}}}^{\mathbf{\text{°}}}\mathbf{\text{<<0}}$ for a reaction, what do you know about the magnitude of K? Of Q?

Step-by-Step Solution

Answer

(a)    The reaction, is not spontaneous in the forward direction and  ${\text{ΔG}}^{\text{°}}$is a relatively large positive value. 

(b)   $\text{K>1}$   and Q depends on initial conditions, not equilibrium conditions, so its value cannot be predicted from  ${\text{ΔG}}^{\text{°}}$.

Step 1: Definition of Concept

Solubility: The maximum amount of solute that can be dissolved in the solvent at equilibrium is defined as solubility.

Constant of soluble product: For equilibrium between solids and their respective ions in a solution, the solubility product constant is defined. In general, the term "solubility product" refers to water-equilibrium insoluble or slightly soluble ionic substances.

 

Step 2: Explain about the sign and magnitude of &#916;G &#176;

(a)

When the equilibrium constant is less than one, it means that very little product is produced in order to achieve equilibrium.

In the forward direction, the reaction is not spontaneous, and   ${\text{ΔG}}^{\text{°}}$is a very large positive value.

Step 3: Explain about the magnitude of K and Q

(b)

The fact that $\text{ΔG}$  is a large negative indicates that the reaction is quite spontaneous and almost complete. At equilibrium, there is far more product than reactant.

As a result, K>1 and Q are determined by initial conditions rather than equilibrium conditions, and their value cannot be predicted using  ${\text{ΔG}}^{\text{°}}$.