ChemCollective-Virtual-Labs/C2/Buffer-Solutions/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this spoken tutorial on Buffer Solutions. |
| 00:05 | In this tutorial we will learn, to prepare 0.5 M Acetate buffer of pH 3.6 and
test the buffering action with small amounts of acid and base. |
| 00:18 | To follow this tutorial you should be familiar with, ChemCollective Vlabs interface. |
| 00:25 | If not, for relevant tutorials please visit our website. |
| 00:30 | Here I am using
Mac OS version 10.10.5 ChemCollective Vlabs version 2.1.0 |
| 00:39 | Java version 8.0. |
| 00:41 | Here I have opened Virtual Chemistry Labs application window. |
| 00:46 | Click on File menu, and select Load homework option.
Default Lab setup dialog box opens. |
| 00:55 | Double-click on Acids and Bases folder.
Click on Buffer Creation Problem. |
| 01:02 | The required chemicals for this experiment are provided in the Stockroom Explorer.
Let me demonstrate how to make Acetate buffer solution. |
| 01:12 | A buffer solution, is composed of a weak acid or weak base and its conjugate salt. |
| 01:19 | Its pH changes very little when a small amount of acid or base is added to it. |
| 01:26 | HendersonâHasselbalch equation is useful for estimating the pH of a buffer solution. |
| 01:33 | Please refer to the excellent tutorial on buffers at the following link. |
| 01:38 | To prepare Acetate buffer of a particular pH, Acetic acid and Sodium acetate are mixed in various proportions. |
| 01:46 | To prepare 50 ml of pH 3.6 Acetate buffer-
We have to mix 46.3 ml of 0.1 M Acetic acid and 3.7 ml of Sodium acetate. |
| 02:01 | Back to the Workbench.
Let us retrieve the chemicals and apparatus required for this experiment. |
| 02:09 | From the Stockroom Explorer click on water, 1M Sodium acetate and 1M Acetic acid. |
| 02:18 | From Glassware cabinet retrieve, 250 ml Erlenmeyer flask, 50 ml graduated cylinder. |
| 02:28 | Make the duplicates of all the apparatus.
Rename graduated cylinders as G1 and G2. |
| 02:39 | Rename Erlenmeyer flasks as A1 and A2. |
| 02:46 | Let us prepare 0.5 M Acetic acid by diluting 1 M Acetic acid. |
| 02:53 | Measure 50 ml of Acetic acid in the graduated cylinder G1. |
| 03:02 | Pour the contents of the graduated cylinder G1 into Erlenmeyer flask A1. |
| 03:11 | Measure 50 ml of water using the same graduated cylinder. |
| 03:18 | Pour water into Erlenmeyer flask A1. |
| 03:24 | Click on flask A1 and note the pH.
It shows a pH of '2.53. |
| 03:32 | Similarly prepare 0.5 M Sodium acetate solution. |
| 03:38 | Measure 50 ml of 1M Sodium acetate solution in graduated cylinder G2. |
| 03:47 | Transfer this solution into Erlenmeyer flask A2. |
| 03:54 | Measure 50 ml of water using the same graduated cylinder. |
| 04:01 | Pour water from graduated cylinder into Erlenmeyer flask A2. |
| 04:08 | Click on flask A2, note the pH.
It shows a pH of 9.23. |
| 04:16 | We now have 0.5 M of Acetic acid and 0.5 M Sodium acetate solutions. |
| 04:23 | Retrieve a 250 ml beaker from the glassware cabinet. |
| 04:28 | Transfer 46.3 ml of 0.5 M Acetic acid into the beaker. |
| 04:35 | Bring flask A1 over to the beaker. |
| 04:39 | Type 46.3 in the Transfer amount input bar.
Click on Pour. |
| 04:46 | Transfer 3.7ml of 0.5 M Sodium Acetate into the beaker. |
| 04:53 | Bring flask A2 over to the beaker. |
| 04:56 | Type 3.7 in the Transfer amount input bar.
Click on Pour. |
| 05:04 | Click on the beaker, check the pH in the PH Meter.
pH is shown as 3.66. |
| 05:13 | We now have an acetate buffer solution of pH 3.66. |
| 05:19 | Rename the beaker with buffer solution as Acetate buffer. |
| 05:25 | Remove the used Erlenmeyer flasks and Graduates cylinders from the Workbench. |
| 05:32 | To test the buffering action,
select water, hydrochloric acid(HCl) and 1M sodium hydroxide(NaOH) from Stockroom Explorer. |
| 05:43 | We will have to dilute, 1M hydrochloric acid(HCl) and 1M sodium hydroxide(NaOH) to 0.1 M hydrochloric acid(HCl) and 0.1 M sodium hydroxide(NaOH). |
| 05:56 | Retrieve two sets of-
10 ml graduated cylinders 250 ml beakers |
| 06:06 | Disposable pipettes from the glassware cabinet. |
| 06:12 | Rename graduated cylinders as G1 and G2. |
| 06:18 | Rename Beakers as A and B |
| 06:22 | Rename Disposable pipette as P1 and P2. |
| 06:28 | Measure 9 ml of water using graduated cylinder G1
Pour it in 250 ml Beaker A. |
| 06:39 | Add 1 ml of 1M HCl to Beaker A using disposable pipette P1. |
| 06:51 | 0.1 M of hydrochloric acid(HCl) is ready for use. |
| 06:57 | Similarly dilute 1M sodium hydroxide(NaOH) with water to prepare 0.1M sodium hydroxide(NaOH). |
| 07:08 | Prepare 0.1 M sodium hydroxide(NaOH) in beaker B, similarly as before. |
| 07:18 | Diluted acid has a pH of 1.
Diluted base has a pH of 13. |
| 07:25 | Let us add a small amount of acid to check the buffering action. |
| 07:30 | Place the disposable pipette over the flask A. |
| 07:34 | Withdraw 0.2 mL of HCl from flask A. |
| 07:40 | Place the pipette over the beaker containing Acetate buffer. |
| 07:45 | Pour 0.2 ml into buffer solution. |
| 07:49 | Observe the change in pH. Notice that there is not much change in pH. |
| 07:57 | Now add small amount of base to the buffer solution. |
| 08:02 | Withdraw 0.2 ml of 0.1 M sodium hydroxide(NaOH) using disposable pipette. |
| 08:09 | Place the pipette over the beaker containing buffer.
Pour 0.2 ml into buffer solution. |
| 08:17 | Observe the pH Meter. Notice that there is no much change in the pH. |
| 08:24 | Add acid and base to the buffer solution a few more times and check the pH. |
| 08:47 | Let us summarize.
In this tutorial we have learnt to, Prepare 0.5 M Acetate buffer of pH 3.6. |
| 08:57 | Tested buffering action with small amounts of hydrochloric acid(HCl) and sodium hydroxide(NaOH). |
| 09:04 | As an assignment, Prepare pH 5.0 Acetate buffer and test with small amounts of acid and base. |
| 09:13 | Hint: use 14.7 ml of 0.5 M Acetic acid and 35.3 ml of 0.5 M Sodium acetate. |
| 09:24 | The video at the following link summarizes the Spoken Tutorial project.
Please download and watch it. |
| 09:32 | The Spoken Tutorial Project team- conducts workshops using spoken tutorials and
gives certificates on passing online tests. For more details, please write to us. |
| 09:43 | Please post your timed queries in this forum. |
| 09:48 | Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
More information on this mission is available at this link. |
| 09:59 | This tutorial is contributed by Snehalatha kaliappan and Madhuri Ganapathi from IIT Bombay
Thank you for joining. |
