AP-S07_Gibbs_Free_Energy

# AP-S07_Gibbs_Free_Energy - 7 The Gibbs Free Energy of the...

This preview shows pages 1–2. Sign up to view the full content.

The Gibbs Free Energy of the Autoionization of Water Purpose In this experiment, you will measure the pH for water at a series of temperatures and calculate the ion product constant, K w ,. With this information, you will calculate the Gibbs free energy for the autoionization of water at each temperature. Introduction The pH of water is determined by the autoionization constant at a given temperature. At 298K, the autoionization constant of water, K w , is 1.0x10 -14 . H 2 O H + + OH - K w = 1.0x10 -14 at 298K Since K w = [H + ][OH - ] = 1.0x10 -14 , [H + ] = [OH - ] = 1.0x10 -7 and pH = -log(1.0x10 -7 )=7.0. However, the value of K w changes with temperature and so does the pH of the water. The enthalpy and entropy changes of the reaction H + + OH - H 2 O are (nearly) independent of temperature. Hence, we can use the change in the pH of pure water as a function of temperature to determine the thermodynamics of this reaction. Let us start with the fact that the equilibrium constant for this reaction is K eq . H

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

### Page1 / 2

AP-S07_Gibbs_Free_Energy - 7 The Gibbs Free Energy of the...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online