Experiment 4 Flashcards
(13 cards)
pH
A measure of the acidity or alkalinity of solution.
pH Meters
Indicate pH by measuring the electromotive fore (emf) developed by a cell, using the solution as an electrolyte.
Buffer
A solution that resists changes in pH. It is a system that maintains a relatively steady H+ concentration by shifting the equilibrium between a conjugate acid-base pair. Made by dissolving almost equal concentrations of a weak acid/base and its conjugate base/acid.
Buffer Ratio
[conjugate base/acid] / [acid/base]
Buffer Capacity
The number of moles of strong acid/base needed to change the pH of one litre of buffer by one unit. The larger it is, the more resistant the buffer is to changes in pH. Is affected by the buffer ratio. The farther the ratio deviates from one, the less buffering capacity the buffer has.
Bronsted-Lowry Acid
A substance the can donate a hydrogen ion (H+).
Bronsted-Lowry Base
A substance that can accept a hydrogen ion (H+).
Lewis Acid
A substance that can accept a pair of electrons.
Lewis Base
A substance that can donate a pair of electrons.
Neutral Solution
[H+] = [OH-] = 1 x 10^-7 and pH = 7 at 25°C.
Acidic Solution
[H+] > 1 x 10^-7 and pH below 7 at 25°C.
Basic Solution
[H+] < 1 x 10^-7 and pH above 7 at 25°C.
Experiment 4 Summary
1) Check to make sure the pH meter is calibrated (a graphic of an electrode beside a bar graph on the top left and a circle square root A on the right).
2) Titrate the weak acid/base with the unknown strong base/acid. Use the pH meter to obtain data points to create a titration curve.
3) Create buffers and add 1 mL increments of NaOH to create a titration curve to find the buffer capacity.