Welcome to this spoken tutorial on Acid-Base Titrations using Vlabs.
In this tutorial we will learn to standardise: Strong-Acid with Strong-Base and Strong-Acid with Weak-Base using titration method.
To follow this tutorial you should be familiar with- ChemCollective Vlabs interface.
If not for relevant tutorials, please visit our website.
Here I am using Mac OS version 10.10.5
ChemCollective Vlabs version 2.1.0 Java version 8.0.
Here I have opened Virtual Chemistry labs application window. Default lab setup window opens.
Let us begin the demonstration with standardization of strong acid with strong base.
We will retrieve required chemicals from stockroom. Double-click on Strong-acids cabinet.
Now double click to Select, 0.1 Molar Hydrochloric acid from the list. Close the cabinet.
From the Strong-bases cabinet, select, 0.1 Molar sodium hydroxide. Close the cabinet.
From the Indicators cabinet select Phenolphthalein.
Drag the bottle and drop on the workbench. Close the cabinet.
Click on Glassware menu. Now select, 250 mL Erlenmeyer Flask.
10 mL Pipet and 50 mL Buret. Rearrange the apparatus.
Rename the Erlenmeyer Flask as A1.
Using pipet transfer 20 mL of Hydrochloric acid(HCl) into flask A1.
Place the 10 mL pipet on flask containing Hydrochloric acid(HCl).
In the Transfer Amount input-bar type 10. Click on Withdraw.
Drag the Pipet on to flask A1.
In the Transfer Amount input-bar type 10. Click on Pour.
We require 20 mL of HCl for this titration.
Since we have 10 mL pipet we need to use it twice to transfer 20 mL of Hydrochloric acid(HCl).
Place Phenolphthalein bottle over Flask A1.
Type 0.3 in the Transfer Amount input bar. Click on pour.
Keep Phenolphthalein bottle and Hydrochloric acid(HCl) aside.
Drag and place 0.1 Molar Sodium hydroxide(NaOH) over the burete.
Transfer 50 mL of Sodium hydroxide(NaOH) into the buret. Observe that, burete reading is not zero.
This is because the lower part of the burete is also filled. Keep Sodium hydroxide(NaOH) flask aside.
Place the burete over Flask A1. Click on the buret.
Note the initial volume of Sodium hydroxide(NaOH) in the buret from the Solution Info panel.
Change the Transfer Bar to Realistic Transfer. Click on Pour button gradually.
Reaction between Hydrochloric acid(HCl) and Sodium hydroxide(NaOH) is equimolar.
So, end point is expected around 20 mL.
To obtain accurate volume for end-point detection; After adding 19 mL of Sodium hydroxide(NaOH), change the Transfer Bar to Significant Figures Transfer.
In the Transfer Amount input bar type 0.01.
This will transfer 0.01 mL of Sodium hydroxide(NaOH) for every click on the pour button.
Observe the pH change in the Solution Info panel.
Click on pour button, observe the faint pink colour in Flask A1. This is the end-point of titration.
Click on the buret. Note the volume of remaining Sodium hydroxide(NaOH) from the solution info panel.
Final calculations are shown on this slide.
We have used the formula M1V1= M2V2 to calculate M1 that is molarity of Hydrochloric acid(HCl).
We have obtained the value of M1 as 0.1 M.
To clear the workbench, select each component .
To remove the selected component, click on remove tool.
Similarly remove all the components from the workbench.
Let us retrieve solutions for the titration of Strong-acid with Weak-base.
Double-click on Strong-acids cabinet and select 1 Molar Hydrochloric acid(HCl). .
Now double click on Weak-bases cabinet and select 1 Molar Ammonia.
For this experiment let us choose methyl orange as indicator.
Drag and place it on the workbench.
Double-click on Glassware menu. Select the following glassware;
250 mL Erlenmeyer Flask. 10 mL Pipet and 50 mL Buret.
Rearrange the apparatus.
Rename the Erlenmeyer Flask as A2.
Change the Transfer Bar to precise transfer.
Using pipet transfer 20 mL of Ammonia into flask A2.
Place 10 mL pipet on flask containing Ammonia.
In the Transfer Amount input-bar type 10. Click on Withdraw.
Drag the Pipet on to flask A2.
In the Transfer Amount input-bar type 10. Click on Pour.
We need 20 mL of Ammonia, so pipette out twice into flask A2.
Transfer 0.3 mL of methyl orange into flask A2. Keep methyl orange bottle aside.
Drag and place 1 M Hydrochloric acid over the buret.
Transfer 50 mL of Hydrochloric acid into the buret.
Place the buret over flask A2.
Let us start the titration.
Change the Transfer Bar to Realistic Transfer. Click on Pour button gradually.
Reaction between Hydrochloric acid(HCl) and ammonia is equimolar. So, end point is expected around 20 mL.
To obtain accurate volume for end-point detection; After adding 19 mL of Hydrochloric acid, change the Transfer Bar to Significant Figures Transfer.
In the transfer amount input bar type 0.01. Click on Pour
This will transfer 0.01 mL of Hydrochloric acid(HCl) for every click on pour button.
As we titrate observe the increase in temperature.
Observe the pH changes.
Transfer a few more drops of Hydrochloric acid(HCl). Observe the change in colour in Flask A2 to orange colour.
Note the final volume of Hydrochloric acid(HCl) from the Solution info panel.
Your final volume may be different from the value shown here.
Click on Spectrometer radio button. Note the Absorbance in the Solution info panel.
Here are the final calculations. Molarity of ammonia is 1M.
Let us summarize . In this tutorial we have learnt to standardise; Strong-Acid with Strong-Base and Strong-Acid with Weak-Base using titration method.
As an assignment, Standardize a solution of ethanoic acid (acetic acid) using titration method.
Hint- All the necessary solutions and apparatus are available in default lab setup window.
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This tutorial is contributed by Snehalatha Kaliappan and Madhuri Ganapathi from IIT-Bombay. Thank you for joining.