ACTIVITY 32 The pH Scale and Buffers Timer: ___________________Manager: _____________________ Recorder/Presenter: __________________Reader: ___________________ Reflector/Quality Control: __________________ Other: __________________ INFORMATION A convenient scale for expressing the acidity or basicity of an aqueous solution is using a logarithmic called pH. The pH of an aqueous solution is defined as follows: pH = -log[H3O + ] where log indicates the logarithm. This is a function on your scientific calculator. The pH value generally ranges from 0 to 14. You also need to remember the autoionization constant of water. Kw = [H+ ][OH- ] = 1.0 10-14 Model 1: The pH Scale Key Questions: 1. Consider the neutral solution on the left in which [H+ ] = [OH- ]. a. Determine [H+ ] for this solution and place it in the model? b. Calculate the pH of a neutral solution and place this value in the model. 2. Consider the vial in the middle vial in which [H+ ] is 2.2 10-5 M. a. Is this solution acidic, basic, or neutral (place your answer on the line in the middle of the vial)? ____________ How do you know? b. Calculate the pH for this solution and place this value in the model. 15 minutes