## Units in answer

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

E_Villavicencio 2N
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

### Units in answer

If we have a reaction such as 2H2O2(l)--->2H2O(l)+O2(g), is the enthalpy of the reaction expressed in kJ/mol, or just kJ? Because the solutions manual adds all the values and expresses them in kJ/mol. Doesn't the mol part cancel out?

Along with this question, if we are given the enthalpy and entropy value of this reaction in kJ/mol, do we have to multiply them by 2 moles or something to calculate the Gibbs free energy? One of the questions in the quiz gave us enthalpy and entropy in kj/mol and J/mol respectively but the reaction had 2 moles of product. This really confused me since I thought units cancelled out.

004583503_Lupe2E
Posts: 10
Joined: Wed Nov 18, 2015 3:00 am

### Re: Units in answer

From my understanding the units are KJ/mol. If you have J/mol just convert to KJ and be specific on the amount of sig figs. It shouldn't cancel out if ur just adding, subtracting, or multiplying. It's only when you are dividing (ex. JK/mol * 1/JK/mol) is when they can "cancel" each other.

E_Villavicencio 2N
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Units in answer

In page 340 of the book, they cancel out the units of entropy when they are adding the quantities because it goes #of moles x Sm(of each substance), and they get a result in J/K

Return to “Gibbs Free Energy Concepts and Calculations”

### Who is online

Users browsing this forum: No registered users and 1 guest