Acid - Base Titrations They are an application of acid-base neutralization reactions that require the use of an indicator. 1

NaOH (aq) + HCl (aq)  NaCl (aq) + H2O (l) Stoichiometry The stoichiometry of an acid-base neutralization reaction is the same as that of any other reaction that occurs in solution (they are double displacement reactions, after all). For example, in the reaction of sodium hydroxide and hydrogen chloride, 1 mol of NaOH neutralizes 1 mol of HCl: NaOH (aq) + HCl (aq)  NaCl (aq) + H2O (l) Stoichiometry provides the basis for a procedure called titration, which is used to determine the concentrations of acidic and basic solutions.

Titration Titration is a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration. If you wish to find the concentration of an acid solution, you would titrate the acid solution with a solution of a base of known concentration. You could also titrate a base of unknown concentration with an acid of known concentration.

Objectives of Titration Practicle One objective of this practicle is to observe differences in shapes of titration curves when various strengths of acids and bases are combined. You will also learn about the function and selection of appropriate acid-base indicators in this experiment. In order to do several other experiments in this lab manual, you need to be able to interpret the shape of a titration curve.

Titration Equipment In the titration of an acid by a base, the Vernier pH sensor placed in measures the pH of the acid solution in the beaker as a solution (analyte) of a base with a known concentration(titrant) is added from the burette.

Titration Procedure A measured volume of an acidic or basic solution of unknown concentration is placed in a beaker. The electrodes of a pH meter are immersed in this solution, and the initial pH of the solution is read and recorded. A burette is filled with the titrating solution of known concentration. This is called the standard solution, or titrant. Measured volumes of the standard solution are added slowly and mixed into the solution in the beaker. The pH is read and recorded after each addition. This process continues until the reaction reaches the equivalence point, which is the point at which moles of H+ ion from the acid equal moles of OH- ion from the base.

Equivalence Point and End Point

Indicators and Titration Curve 9

Strong Acid – Strong Base Titration

High resolution touch screen 12.8 cm, 800 x 480 pixel resolution Designed for both stylus and touch Wide viewing angle for lab groups Full sensor support Compatible with all Vernier sensors Faster analysis Quick response to touch, curve fits and modelling

Built-in sensors GPS 3-axis accelerometer Ambient temperature Light Microphone Fast data collection 100,000 samples per second Rechargeable batteries High-capacity, lithium-ion rechargeable battery Wireless connectivity Wi-Fi Bluetooth

References http://inds.co.uk/education/labquest2.htm Performing a Titration - YouTube http://www.youtube.com/watch?v=YDzzMcrdyB4 Acid-Base Titration (LabQuest) http://www.youtube.com/watch?v=3P8FPsbseqM http://www.chembio.uoguelph.ca/educmat/chm19104/chemtoons/