## Drawing and labeling reaction profile

Jacob Afable 3J
Posts: 41
Joined: Fri Sep 25, 2015 3:00 am

### Drawing and labeling reaction profile

4.35 says to draw and label the reaction profile for the reaction: CH3Br + -OH $\rightleftharpoons$ CH3OH + Br-.

For this particular reaction, how do we know that the Gibbs free energy of the reaction between the reactants and products is negative?

For other reactions, how will we know whether $\Delta$G will be positive or negative between the reactants and products?

Alli Foreman 2H
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

### Re: Drawing and labeling reaction profile

$\Delta G_{r}$ is equal to $\Delta G_{products} - \Delta G_{reactants}.$

If the graph's final point is below the initial point, then that means that $\Delta G_{products} < \Delta G_{reactants}$ and therefore $\Delta G_{r}$ will be negative.

If the graph's final point is above the initial point, then that means that $\Delta G_{products} > \Delta G_{reactants}$ and therefore $\Delta G_{r}$ will be positive.

Jacob Afable 3J
Posts: 41
Joined: Fri Sep 25, 2015 3:00 am

### Re: Drawing and labeling reaction profile

Alli Foreman 2H wrote:$\Delta G_{r}$ is equal to $\Delta G_{products} - \Delta G_{reactants}.$

If the graph's final point is below the initial point, then that means that $\Delta G_{products} < \Delta G_{reactants}$ and therefore $\Delta G_{r}$ will be negative.

If the graph's final point is above the initial point, then that means that $\Delta G_{products} > \Delta G_{reactants}$ and therefore $\Delta G_{r}$ will be positive.

How about for $\Delta$G$\circ$$\neq$

Alli Foreman 2H
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

### Re: Drawing and labeling reaction profile

$\Delta G\neq ^{\circ}$ is always positive. It is the difference between the $\Delta G$ of the reactants and the $\Delta G$ of the intermediates. $\Delta G$ intermediates is always above $\Delta G$ reactants (think of the graph, it's always a hill shape).
So $\Delta G$ of the intermediates - $\Delta G$ of the reactants is always positive.