## Equations: ln Q vs. log Q [ENDORSED]

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

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

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

Rakhi Ratanjee 1D
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am

### Equations: ln Q vs. log Q

Some of the thermodynamic equations have log Q and some have ln Q. Are these functions interchangeable or do we just have to apply whichever function the equation specifies?

sahiltelang-Discussion 1J
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am

### Re: Equations: ln Q vs. log Q

lnQ and logQ are conceptually the same yet matematically not. ln is the natural log or log base e whiles log is just log base 10. Thermo equations use log sometimes when dealing with ph's as it makes it easier to solve for pH or pOH rather than needing to convert between ln and log. You can calculate using either method, yet just keep in mind that you will need to multiply a constant along when using log.

Shane Simon 2K
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

### Re: Equations: ln Q vs. log Q

ln and log are not interchangeable. Using ln will give you a different answer than using log. Be sure to apply whatever function the equation uses. As Sahil mentioned, you technically could use ln or log instead of the one in the equation but you would need to use the conversion factor of ln(X) = 2.303log(X) (which is given on the constants and equations sheet) to get the right answer. But instead of going through all of that it is just much easier and quicker to just use the function that the equation says.

Ivy Lu 1C
Posts: 54
Joined: Thu Jul 27, 2017 3:00 am

### Re: Equations: ln Q vs. log Q  [ENDORSED]

They are not interchangeable. If you want to use log instead of ln then remember that ln(X) = 2.303log(X). If an equation has ln, then you should use ln. If an equation has log, then you should use log. This way it's easier to avoid error.

204932558
Posts: 23
Joined: Fri Sep 29, 2017 7:05 am

### Re: Equations: ln Q vs. log Q

log and ln are not the same. Ln(x) = 2.303log(x)

Justin Bui 2L
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

### Re: Equations: ln Q vs. log Q

They're "interchangeable" in the sense that you can choose to use log or ln but they're right in saying there is a difference in how you use each one, so you can't just substitute one with the other plainly. ln(X) = 2.303log(X) is the biggest thing to remember when deciding which path to take.