Difference between revisions of "ChemCollective-Virtual-Labs/C2/Dilutions-and-pH-Measurement/English"

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Revision as of 14:21, 19 December 2016

Visual Cue Narration
Slide Number 1

Title Slide

Welcome to this tutorial on Dilutions and pH measurement.
Slide Number 2

Learning Objectives


In this tutorial, we will learn to measure:
  • Change in pH for solutions of acid and base on dilution.
  • Variation in pH by common-ion effect for weak acids and bases.


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.
Slide Number 5

Measurement of pH


10 Times Dilution:

0.1 M HCl to 0.01 M Hcl


0.1M NaOH to 0.01 M NaOH.


2 ml of 0.1 M HCl or NaOH is diluted to 20 ml with distilled water.
 For this demonstration, let us dilute -


  • 0.1 molar Hydrochloric acid to 0.01 molar Hydrochloric acid.
  • 0.1 molar sodium hydroxide to 0.01 molar sodium hydroxide.

For this experiment,

2 ml of 0.1 M Hydrochloric acid or sodium hydroxide is diluted to 20 ml with distilled water.

Click on Vlabs folder to open.

Double-click on vlabs.exe file.

I have opened a “Virtual Chemistry labs” application window.
Cursor on Stockroom explorer .


Double-click on Strong-acid cabinet .


Stockroom explorer opens with solutions of various acids and bases.


Double-click on Strong-acids cabinet.


A list of acidic solutions with various strengths opens.

Double-click to choose 0.1 Molar HCl.


Click on the flask, observe the pH in the pH Meter.


Click on the radio button near Strong-acids cabinet, to close the list.

Do Double-click to choose 0.1 Molar HCl.


Click on the flask, observe the pH on the pH Meter.


Note that pH Meter reads 1.


Click on the radio button near Strong-acids cabinet, to close the list.

From Stockroom explorer, Double-click on Strong-bases cabinet.


Double-click to choose 0.1 Molar NaOH.


Next, from Stockroom explorer, double-click on Strong-bases cabinet.


A list of basic solutions with various strengths opens.


Double-click to choose point one molar NaOH.

Click on the flask, observe the pH in the pH Meter.


Point to the pH Meter.


Click on the radio button.

Click on the flask, observe the pH on the pH Meter.


Note that pH Meter reads 13.


Click on the radio button near Strong-bases cabinet to close the list.

Double click on distilled water from Stockroom explorer panel. Double click on Distilled water icon from Stockroom explorer.
Cursor on the workbench. Let us now add the required apparatus to the workbench.
Click on glassware icon.


Select Graduated Cylinders.


From the sub-menu, select 10 mL Graduated Cylinder.

Click on glassware icon.


Select Graduated Cylinders.


From the sub-menu, select 10 mL Graduated Cylinder to add to the workbench.

Right-click on the Graduated Cylinder.


From the context menu, select copy.

Move the cursor to a different position.


Right-click and choose Paste option from the menu.

For this experiment, we need two Graduated cylinders.


Right-click on the Graduated Cylinder.


From the context menu, select copy.


Place the cursor at a different place.


Right-click and choose Paste option from the menu.


Click on glassware icon.


Select Erlenmeyers.


From the sub-menu select 250 mL Erlenmeyer Flask.


Copy and paste the flask using context menu.

Click on glassware icon.


Select Erlenmeyers.


From the sub-menu, select 250 mL Erlenmeyer Flask.


We require two flasks.

Right-click to copy and paste.



Right-click on Graduated Cylinder, from the Context-menu select Rename option.


Type A in the text box and click Ok button.

Label the Graduated Cylinders as A and B.

Right-click on the Graduated Cylind er.

From the Context-menu, select Rename option.


A text box opens. Type A in the text box and click on Ok button.

Similarly, label the other Cylinder as B.


Similarly, label Erlenmeyer Flasks as A and B..

Drag and place the apparatus on different positions on the workbench.


Place each set of apparatus at a different position on the workbench.


Use set A for acids and set B for bases.

2 ml of 0.1 M HCl


To perform this experiment, we will dilute 2 ml of 0.1 M HCl with 18 ml of distilled water.
Drag 0.1 molar Hydrochloric acid flask over to Graduated Cylinder A.


In the transfer amount input bar type, 2.

Click on Pour.

Drag 0.1 molar Hydrochloric acid flask over to the Graduated Cylinder A.


In the Transfer amount input bar, type 2.

Click on Pour.


Move the flask aside.

Drag distilled water tank over flask A.


In the transfer amount input bar type, 18.


Click on Pour.


Move the Distilled water aside.

Move the Distilled water tank over Flask A.


In the Transfer amount input bar, type 18.


Click on Pour.


Move the Distilled water aside.


Place the Graduated Cylinder A over Flask A.

Change the transfer mode to realistic transfer.


Click on pour gradually.


Place the Graduated Cylinder A over Flask A.


Change the transfer mode to Realistic transfer.

Click on Pour button gradually.


Move the Graduated Cylinder A aside.

Click on Flask A and observe the pH on the pH meter. Click on Flask A, observe the pH on the pH meter.

pH meter reads 2.

Cursor on the workbench. Similarly, let us dilute 0.1 Molar NaOH and measure pH.
Drag 0.1 molar Sodium Hydroxide flask over to Graduated Cylinder B.


Tools >>Transfer bar>>Precise transfer.


In the transfer amount input bar type, 2.

Click on Pour.

Measure 2 mL of 0.1 M NaOH in Graduated Cylinder B.


Drag 0.1 molar Sodium Hydroxide flask over to Graduated Cylinder B.


Using Tools menu, change the transfer mode to Precise transfer.


In the transfer amount input bar, type 2.

Click on Pour.


Move the flask aside.

Move Distilled water tank over Flask B.


In the transfer amount input bar, type 18.


Click on Pour.


Move the Distilled water tank over Flask B.


In the Transfer amount input bar, type 18.


Click on Pour.


Move the Distilled water aside.

Transfer 2 ml of NaOH from the Graduated

Cylinder B to Flask B.


Tools >>Transfer bar>>Realistic transfer.


Click on Pour button gradually.

Transfer 2 ml of sodium hydroxide from Graduated Cylinder B to Flask B.


Place the Graduated Cylinder B over Flask B.


Change the transfer mode to realistic transfer.


Click on Pour button gradually.


Move the Graduated Cylinder B aside.

Click on Flask B and observe the pH on the pH meter. Click on Flask B, observe the pH on pH meter.

pH meter reads 12.

Slide Number 6

Results

Concentration pH pH after dilution
0.1M HCl 1.0 2.0
0.1M NaOH 13.0 12.0

pH is a logarithmic scale, for every 10 times dilution pH changes by 1 unit.

Here is a table which shows results of our experiment.


pH of 0.1 M Hydrocholric acid is 1. When diluted, acidity decreases.

After dilution, pH was found to be 2.


Similarly, pH of 0.1 M NaOH is 13. When diluted, alkalinity decreases.


Hence, after dilution, pH was found to be 12.


Since pH is a logarithmic scale, for every 10 times dilution pH changes by 1 unit.

File >> New Workbench. Back to the workbench.

For the next experiment, load a new workbench using File menu.

Click on Workbench 2.

Cursor on Workbench 2. Now let us study the variation in pH by common ion effect.


We will demonstrate this, using weak acids and weak bases.

Slide Number 7


Common ion effect


1. Ethanoic acid and its conjugate base, sodium ethanoate.


2. Ammonia and its conjugate acid, Ammonium Chloride.

For this demonstration , we will use two examples-


1. Ethanoic acid and its conjugate base, sodium ethanoate.


2. Ammonia and its conjugate acid, Ammonium Chloride.

Cursor on the workbench. Back to workbench.


Place the required chemicals from the Stockroom explorer on the workbench.

From Stockroom explorer, Double-click on Weak-acids cabinet.


Double-click to choose 1M Ethanoic acid.


Click on the small button next to Weak-acids cabinet.

From Stockroom explorer, double-click on Weak-acids cabinet.


A list of weak acid solutions with various strengths opens.


Double-click to choose 1 molar Ethanoic acid.

Close the list.

Again from Stockroom explorer, Double-click on Weak-bases cabinet.


Double-click to choose 1 molar Ammonia.

Again from Stockroom explorer, double-click on Weak-bases cabinet.


A list of weak bases with various strengths opens.


Double-click to choose 1 molar Ammonia solution.

Close the list.

Double-click on Conjugate-acid folder,


Double-click on 1M Ammonium Chloride.

Double-click on Conjugate-acids cabinet.


Double-click on 1 molar Ammonium Chloride solution.


Close the list.

Double-click on Conjugate-base folder.


Double-click on 1 molar Sodium Ethanoate.

Double-click on Conjugate-bases cabinet.


Double-click on 1 molar Sodium Ethanoate solution from the list.

Close the list.

Click on new glassware icon and select 250 ml beaker.


Right-click to Copy and paste.

Next, click on new glassware icon. select 250 ml Beaker.

We need 4 Beakers for this experiment.


Right-click on the Beaker.


Using copy and paste option make 3 copies of the Beaker.

Right-click on Beaker, from the Context-menu select Rename option.


Text box opens, type A in the text box and click OK button.

Label the beakers as A, B, C and D.



Drag and place the Beakers A and B to one side of the workbench.


Drag and place the Beakers C and D on other side of the workbench.

Place the Beakers A and B to one side of the workbench.


Place the Beakers C and D on other side of the workbench.

Drag and place Ethanoic acid and its conjugate base, Sodium Ethanoate on one side.


Drag and place Ammonia and its conjugate acid Ammonium Chloride on the other side.

Place Ethanoic acid and its conjugate base, Sodium Ethanoate on one side.


Place Ammonia and its conjugate acid Ammonium Chloride on the other side.

Tools >>Transfer bar>>Precise transfer.


Place 1M Ethanoic acid over beaker A.

Type 25 in the Transfer amount input bar.


Click on pour.


Do the same for beaker C.

Transfer 25 ml of Ethanoic acid in beakers A and B using Precise transfer mode.


Type 25 in the transfer amount input bar.

Click on pour.


Similarly, transfer 25 ml of Ethanoic acid to beaker B.


Move the flask aside.

Place 1M Ammonia solution over beaker B.

Type 25 in the Transfer amount input bar.


Click on pour.


Do the same for beaker D.

Transfer 25 ml of Ammonia solution into beakers C and D.


Move the flask aside.

Place 1M Sodium acetate over beaker C.

Type 25 in the transfer text bar.


Click on pour.

To demonstrate the effect of common ion-


Transfer 25 ml of Sodium ethanoate into beaker B.


Place 1 molar Sodium ethanoate flask over beaker B.


Type 25 in the transfer amount input bar.


Click on pour.


Keep the flask aside.

Click on beaker A.


Observe pH meter.

To check the pH of 1M Ethanoic acid present in beaker A, click on beaker A.

pH meter shows pH value of 2.38.

Click on beaker C.

Observe pH meter.

Click on beaker B.

pH meter shows pH value of 4.76 .

Place 1M Ammonium Chloride flask over beaker D.

Type 25 in the transfer amount input bar.


Click on pour.

Now transfer 25 ml of Ammonium Chloride into beaker D.

Place 1 Molar Ammonium Chloride flask over beaker D.

Type 25 in the transfer amount input bar.

Click on pour.

Keep the flask aside.

Click on beaker B.


To check the pH of 1molar Ammonia present in beaker C, click on beaker C.

pH meter shows pH value of 11.62.

Click on beaker D.


Observe pH meter.

Click on beaker D.

pH meter shows pH value of 9.25.

Now, let us tabulate the results.

Slide Number


Results


Solution pH Solution pH
1 M Ethanoic acid 2.38 1 M Ethanoic acid +1M sodium ethanoate 4.76
1 M Ammonia 11.62 1 M Ammonia + 1 M Ammonium chloride 9.25

Point to the result.

Due to the presence of common ion

that is ethanoate ion, ionization of ethanoic acid decreases.


Hence pH value increases.


Similarly, due to the presence of ammonium ion, ionization of Ammonia decreases.

Hence pH value decreases.

Slide Number

Summary


we have learnt to measure-


  • Change in pH for solutions of 0.1 Molar Hydrochloric acid and 0.1 Molar Sodium Hydroxide on dilution.
  • Variation in pH by common-ion effect for ethanoic acid and ammonia solutions.


Let us summarize.

In this tutorial, we have learnt to measure-


  • Change in pH for solutions of 0.1 Molar Hydrochloric acid and 0.1 Molar Sodium Hydroxide on dilution.
  • Variation in pH by common-ion effect for ethanoic acid and ammonia solutions.


Slide Number

Assignment


Measure change in pH for-


1 M and 0.01 M Sulphuric acid.


1 M and 0.01 M sodium hydroxide.

As an assignment:

Measure change in pH for-


1 M and 0.01 M Sulphuric acid.


1 M and 0.01 M Sodium hydroxide.



Slide Number13:

About Spoken Tutorial project

The video at the following link summarizes the Spoken Tutorial project.


Please download and watch it.

Slide Number14:

Spoken Tutorial workshops

The Spoken Tutorial Project team:

* conducts workshops using spoken tutorials and

  • * gives certificates on passing online tests.

For more details, please write to us.

Slide Number 15:

Forum for specific questions:


Do you have questions in THIS Spoken Tutorial?

  • Please visit this site
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  • Explain your question briefly
  • Someone from our team will answer them


Please post your timed queries in this forum.
Slide Number 17:

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

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