Acid and Base Titration

Acid and Base Titration - Elena Maxim 4 Hr Ap Chem...

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Elena Maxim 4 th Hr Ap Chem 3/31/2008 Titration of a Diprotic Acid: Identifying an Unknown I. Purpose: The purpose of this lab was to identify the identity of an unknown acid by using its molecular weight. The process of titration, which emphasizes several concepts important to solution chemistry and acid-base equilibrium, determines this molecular weight. Titrations are careful procedures used in chemistry to determine the concentration of a particular solution. A solution containing a known concentration of base, called the standard solution, is slowly added to the acid until a neutralization reaction occurs between the two. The point at which stoichiometrically equivalent quantities are brought together is called the equivalence point of the titration. II. Procedure: Method: Measuring the Volume using a Buret 1. About 0.120 g of the unknown diprotic acid is weighed and its mass recorded to the nearest 0.001 g in the data table. This acid is then transferred to a 250 mL beaker and dissolved in 100 mL of distilled water. 2. The beaker is placed on a magnetic stirrer and a stirring ba r is added. Using a utility clamp to suspend a pH sensor on a ring stand, the pH
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Elena Maxim 4 th Hr Ap Chem 3/31/2008 sensor is positioned in the acid solution and is adjusted to face the outside of the beaker. The magnetic stirrer is placed on a medium-stirring rate. 3. Approximately 30 mL of 0.1 M NaOH solution is placed in the burette, after it was first used to coat it. The precise concentration of the NaOH solution is recorded. After the burette is filled, a small amount of the NaOH solution is drained into the beaker and the tip reads precisely 0.00 mL. 4. The pH sensor is then connected to a computer interface and the computer is prepared for the data collection using an existing file in Logger Pro. 5. The titration now begins following these steps: a.) Before adding any NaOH titrant, the collect button is hit and the pH is monitored for 5-10 seconds. Keep is pressed once the pH has stabilized. “0” is typed in the edit box because 0 drops have been added to the acid, Enter is pressed to keep the data. b.) Enough NaOH is added to raise the pH of the solution by 0.20 units. Again when the ph stabilizes the buret reading is recoded and the data is kept. NaOH is added in this way until a pH of 3.5 is reached. c.) At a 3.5 pH, the titration goes by two-drop increments, until the pH is at 4.5. There lager increments of 0.2 units are used. When a pH of 7.5 is reached, the titration goes by two-drop increments, and each buret reading is entered.
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Elena Maxim 4 th Hr Ap Chem 3/31/2008 d.) When a pH of 10 is reached, larger increments to raise the pH by 0.20 units are added. This continues until a pH of 11 is reached. 6.
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This note was uploaded on 05/25/2010 for the course CHEM 101 taught by Professor Fricke during the Spring '10 term at Canisius College.

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Acid and Base Titration - Elena Maxim 4 Hr Ap Chem...

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