ChemCollective-Virtual-Labs/C2/Buffer-Solutions/English

Visual Cue	Narration
Slide Number 1 Title Slide	Welcome to this spoken tutorial on Buffer Solutions.
Slide Number 2 Learning Objectives	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.
Slide Number 3 Pre-requisites www.spoken-tutorial.org	To follow this tutorial you should be familiar with, ChemCollective Vlabs interface. If not, for relevant tutorials please visit our website.
Slide Number 4 System Requirement	Here I am using Mac OS version 10.10.5 ChemCollective Vlabs version 2.1.0 Java version 8.0.
Point to the window.	Here I have opened Virtual Chemistry Labs application window.
File >> Load homework >>Default lab setup dialog box. Double-click on Acids and Bases folder. Select Buffer Creation Problem.	Click on File menu, select Load homework option. Default Lab setup dialog box opens. Double-click on Acids and Bases folder. Click on Buffer Creation Problem.
Point to the chemicals in Stockroom Explorer.	The required chemicals for this experiment are provided in the Stockroom Explorer. Let me demonstrate how to make Acetate buffer solution.
Slide Number 5 Buffer Solutions	A buffer solution, is composed of a weak acid or weak base and its conjugate salt. Its pH changes very little when a small amount of acid or base is added to it.
Slide Number 6 Henderson–Hasselbalch Equation pH = pKa+ log {[A-] / [HA]}	Henderson–Hasselbalch equation is useful for estimating the pH of a buffer solution.
Slide Number 7 Buffer Solutions-Tutorial	Please refer to the excellent tutorial on buffers at the following link. http://chemcollective.org/activities/tutorials/buffers/buffers1
Slide Number 8 Acetate Buffer Solution	To prepare Acetate buffer of a particular pH, Acetic acid and Sodium acetate are mixed in various proportions. To prepare 50 ml of pH 3.6 Acetate buffer- We have to mix 46.3 ml of 0.5 molar Acetic acid and 3.7 ml of 0.5 molar Sodium acetate.
Click on Workbench tab.	Back to the Workbench. Let us retrieve the chemicals and apparatus required for the experiment.
From the Stockroom Explorer click on water, 1M Sodium acetate and 1M Acetic acid.	From the Stockroom Explorer click on water, 1M Sodium acetate and 1M Acetic acid.
Click on Glassware icon. Click on Erlenmeyer flask, select 250 ml Erlenmeyer flask. Click on Graduated cylinder. Click on 50 ml graduated cylinder.	From Glassware cabinet retrieve, 250 ml Erlenmeyer flask, 50 ml graduated cylinder.
Right-click on the graduated cylinder, select duplicate. Right-click on the graduated cylinder select rename. Rename as G1 and G2.	Make the duplicates of all the apparatus. Rename graduated cylinders as G1 and G2.
Right-click on the Erlenmeyer flasks, select duplicate. Right-click on the Erlenmeyer flasks, select rename. Rename as A1 and A2.	Rename Erlenmeyer flasks as A1 and A2.
Cursor on the Workbench.	Let us prepare 0.5 M Acetic acid by diluting 1 M Acetic acid.
Place 1M Acetic acid flask over graduated cylinder G1 . Type 50 in the input bar for Precise transfer mode. Click on Pour. Bring the graduated cylinder over Erlenmeyer flask A1. Type 50 in the input bar for Precise transfer mode. Click on Pour.	Measure 50 ml of Acetic acid in the graduated cylinder G1. Pour the contents of the graduated cylinder G1 into Erlenmeyer flask A1.
Place flask of water over graduated cylinder G1. Type 50 in the input bar for Precise Transfer mode. Click on Pour. Bring the graduated cylinder over Erlenmeyer flask A1. Type 50 in the input bar for Precise transfer mode. Click on Pour.	Measure 50 ml of water using the same graduated cylinder. Pour water into Erlenmeyer flask A1.
Click on flask A1. Point towards pH meter.	Click on flask A1 and note the pH. It shows a pH of '2.53'.
Place 1M Sodium acetate flask over graduated cylinder G2. Type 50 in the input bar for Precise Transfer mode. Click on Pour.	Similarly prepare 0.5 M Sodium acetate solution. Measure 50 ml of 1M Sodium acetate solution in graduated cylinder G2.
Bring the graduated cylinder over Erlenmeyer flask A2. Type 50 in the input bar for Precise Transfer mode. Click on Pour.	Transfer this solution into Erlenmeyer flask A2.
Place flask of water over graduated cylinder G2. Type 50 in the input bar for Precise transfer mode. Click on Pour. Bring the graduated cylinder over Erlenmeyer flask A2. Type 50 in the input bar for Precise transfer mode. Click on Pour.	Measure 50 ml of water using the same graduated cylinder. Pour water from graduated cylinder into Erlenmeyer flask A2. Click on flask A2, note the pH. It shows a pH of 9.23.
Click on the Flasks and show Solution Info Panel.	Now we have 0.5 M of Acetic acid and 0.5 M Sodium acetate solutions.
Click on glassware icon. Click on Beakers, select 250 ml Beaker. Bring flask A1 over to the beaker. Type 46.3 in the transfer amount input bar. Click on Pour. Bring flask A2 over to the beaker. Type 3.7 on the Transfer amount input bar. Click on Pour.	Retrieve a 250 ml beaker from the glassware cabinet. Transfer 46.3 ml of 0.5 M Acetic acid into the beaker. Bring flask A1 over to the beaker. Type 46.3 in the Transfer amount input bar. Click on Pour. Transfer 3.7ml of 0.5 M Sodium Acetate into the beaker. Bring flask A2 over to the beaker. Type 3.7 in the Transfer amount input bar. Click on Pour.
Click on the beaker. Cursor on the pH meter.	Click on the beaker, check the pH in the PH Meter. pH is shown as 3.66. We now have an acetate buffer solution of pH 3.66.
Right-click and click on Rename. Text box opens. In the text box type Acetate buffer	Rename the beaker with buffer solution as Acetate buffer.
Select and Delete the apparatus.	Remove the used Erlenmeyer flasks and Graduates cylinders from the Workbench.
From the Stockroom Explorer, click on 1M HCl and 1M NaOH.	To test the buffering action, select water, 1M HCl and 1M NaOH from Stockroom Explorer. 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).
Select glassware and click on Delete button. Click on glassware cabinet. Click on graduated cylinders from the list select 10 ml graduated cylinder. Click on Pipettes. Select disposable pipette from the list.	Retrieve two sets of- 10 ml graduated cylinders 250 ml beakers Disposable pipettes from the glassware cabinet.
Right-click on the graduated cylinder select Rename. Rename as G3 and G4.	Rename graduated cylinders as G1 and G2.
Right-click on the beaker, select Rename. Rename as A and B.	Rename Beakers as A and B
Right-click on the Disposable pipette, select Rename. Rename as P1 and P2.	Rename Disposable pipette as P1 and P2.
Place flask of water over graduated cylinder G3. Type 9 in the input bar for Precise transfer mode. Click on Pour. Bring the graduated cylinder over Beaker B. Type 9 in the input bar for Precise transfer mode. Click on Pour.	Measure 9 ml of water using graduated cylinder G1 Pour it in 250 ml Beaker A.
Place disposable pipette over 1M HCl. Type 1 in the transfer amount input bar. Click on withdraw. Place the disposable pipette over Beaker B1. Type 1 in the transfer amount input bar. Click on Pour. pH of 0.1 M HCl is 1	Add 1 ml of 1M HCl to Beaker A using disposable pipette P1. 0.1 M of hydrochloric acid(HCl) is ready for use.
Place flask of water over graduated cylinder G3. Type 9 in the input bar for Precise transfer mode. Click on Pour. Bring the graduated cylinder over Beaker B. Type 9 in the input bar for Precise transfer mode. Click on Pour. Place disposable pipette over 1M NaOH. Type 1 in the transfer amount input bar. Click on Withdraw. Place the disposable pipette over Beaker B1. Type 1 in the transfer amount input bar. Click on Pour.	Similarly dilute 1M sodium hydroxide(NaOH) with water to prepare 0.1M sodium hydroxide(NaOH). Prepare 0.1 M sodium hydroxide(NaOH) in beaker B, similarly as before. Diluted acid has a pH of 1. Diluted base has a pH of 13.
Cursor on the workbench.	Let us add a small amount of acid to check the buffering action.
Place the disposable pipette over the 0.1 M HCl beaker. Type 0.2 in the transfer amount input bar. Click on Withdraw. Place the pipette over the beaker containing buffer. Type 0.2 in the transfer amount input bar. Click on Pour.	Place the disposable pipette over the flask A. Withdraw 0.2 mL of HCl from flask A. Place the pipette over the beaker containing Acetate buffer. Pour 0.2 ml into buffer solution.
Point to the pH meter.	Observe the change in pH. Notice that there is not much change in pH.
Place the disposable pipette over the 0.1 M NaOH beaker. Type 0.2 in the transfer amount input bar. Click on Withdraw. Place the pipette over the beaker containing buffer. Type 0.2 in the transfer amount input bar. Click on pour.	Now add small amount of base to the buffer solution. Withdraw 0.2 ml of 0.1 M sodium hydroxide(NaOH) using disposable pipette. Place the pipette over the beaker containing buffer. Pour 0.2 ml into buffer solution.
Point to the pH meter.	Observe the pH Meter. Notice that there is no much change in the pH. Add acid and base to the buffer solution a few more times and check the pH.
Slide Number 9 Summary	Let us summarize. In this tutorial we have learnt to, Prepare 0.5 M Acetate buffer of pH 3.6. Tested buffering action with small amounts of hydrochloric acid(HCl) and sodium hydroxide(NaOH).
Slide Number 10 Assignment	As an assignment, Prepare pH 5.0 Acetate buffer and test with small amounts of acid and base. Hint: use 14.7 ml of 0.5 M Acetic acid and 35.3 ml of 0.5 M Sodium acetate.
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Slide Number 14 Acknowledgement	Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at this link.
	This tutorial is contributed by Snehalatha kaliappan and Madhuri Ganapathi from IIT Bombay Thank you for joining.

Contributors and Content Editors

Madhurig, Snehalathak