Difference between revisions of "ChemCollective-Virtual-Labs/C2/Buffer-Solutions/English"

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(Created page with " Visual cue Narration Slide Number 1 Title slide Welcome to this tutorial on pH scale using interactive PhET simulation. Slide Number 2 Learning objectives we will learn- How...")
 
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Visual cue
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{| border =1
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Narration
+
||'''Time'''
−
Slide Number 1
+
||'''Narration'''
−
Title slide
+
|-
−
Welcome to this tutorial on pH scale using interactive PhET simulation.
+
||'''Slide Number 1'''
−
Slide Number 2
+
−
Learning objectives
+
−
we will learn-
+
−
How to use interactive PhET simulation, pH scale.
+
−
Slide Number 3
+
−
Pre-requisites
+
−
To follow this tutorial,
+
−
Learners should be familiar with topics in high school science subject.
+
−
Slide Number 4
+
−
System Requirements
+
−
Here I am using-
+
−
Ubuntu linux OS version 14.04
+
−
Java version 1.7.0
+
−
Firefox Web Browser version 53.02.2
+
−
Slide Number 5
+
−
Learning Goals
+
−
Using this simulation we will be able to learn-
+
−
pH of solution
+
−
Determine acidity or basicity of solution on the basis of pH
+
−
Place acids and bases in relative order.
+
−
Effect of dilution on pH of solution.
+
−
Logarithmic and linear scale.
+
−
Determine the concentarion of hydroxide, hydronium and water at a given pH
+
−
Slide Number 6
+
−
pH of solution.
+
−
PH scale -
+
−
It is numeric scale used to specify the acidity or basicity of an aqueous solution.
+
−
PH is a measure of hydrogen ion concentration in mol/L.
+
  
−
PH is the negative logarithm of base 10 of  hydrogen ion concentration.
+
'''Title Slide'''
−
from the definition pH can be written as,
+
||Welcome to this spoken tutorial on '''Buffer Solutions'''.
−
pH = - log[H+]
+
|-
−
-----------
+
||'''Slide Number 2'''
−
For acidic solution, pH < 7
+
−
Ex: Hcl(10-2) will have a pH = 2
+
−
For basic solution, pH > 7
+
−
Ex: NaOH(10-12) will have a pH=12
+
−
For neutral solution, pH = 7
+
  
 +
'''Learning Objectives'''
  
−
Slide Number 7
+
||In this tutorial we will learn,
−
Link for PhET simulation
+
  
−
http://phet.colorado.edu
+
to prepare 0.5 M '''Acetate buffer''' of pH 3.6 and, 
−
pH simulation is given as code file along with this tutorial.
+
  
−
Use the given link to download
+
test the buffering action with small amounts of acid and base.
 +
|-
 +
||'''Slide Number 3'''
  
−
http://phet.colorado.edu
+
'''Pre-requisites'''
−
Cursor on the interface.
+
−
This is the interface for pH simulation
+
−
Point to each screen.
+
−
The interface has three screens-
+
−
Macro
+
−
Micro
+
−
My solution
+
  
−
Cursor on Macro screen.
+
'''www.spoken-tutorial.org'''
 +
||To follow this tutorial you should be familiar with,
  
−
Let us begin our simulation with Macro screen.
+
'''ChemCollective Vlabs interface'''.
−
Click on Macro screen to open it.
+
−
Cursor on Macro screen.
+
−
Cursor on pH scale.
+
−
Point to green probe.
+
  
−
Point to pH meter.
+
If not, for relevant tutorials please visit our website.
 +
|-
 +
||'''Slide Number 4'''
  
 +
'''System Requirement'''
 +
||Here I am using
  
−
This screen has-
+
Mac OS version 10.10.5
−
pH scale at the left of screen.
+
−
Green probe attached to pH scale ro measure pH.
+
−
PH meter to show pH.
+
  
 +
ChemCollective Vlabs version 2.1.0
  
−
Cursor on water pump.
+
Java version  8.0
−
Cursor on water canter.
+
|-
−
Point to pump.
+
||Point to the window.
−
Water pump at the right of screen to add water.
+
||Here I have opened '''Virtual Chemistry Labs''' application window.
−
Water canter with tap for the solution .
+
|-
−
Pump to remove solution attached to right bottom of the canter.
+
||'''File''' >> '''Load homework''' >>'''Default lab setup''' dialog box.
−
Point to Dropper.
+
  
−
Cursor on Drop Downbox.
+
Double-click on '''Acids and Bases''' folder.
−
Dropper at the top of the container to add more liquid.
+
−
At the top middle of screen has Drop Downbox to choose one of the liquid.
+
  
−
Point to Reset Button.
+
Select '''Buffer Creation Problem'''.
−
A Reset Button is provided at the right hand side bottom corner.
+
||Click on '''File''' menu, select '''Load homework''' option.
  
−
Click on Black arrow.
+
'''Default Lab setup''' dialog box opens.  
  
−
cursor on Battery acid and click
+
Double-click on '''Acids and Bases''' folder.
  
−
Point to canter.
+
Click on '''Buffer Creation Problem'''.  
−
Point to dropper
+
|-
 +
||Point to the chemicals in '''Stockroom Explorer'''.
 +
||The required chemicals for this experiment are provided in the '''Stockroom Explorer'''.
  
−
By default chicken soup is selected.
+
Let me demonstrate how to make '''Acetate buffer''' solution.
−
Click on black arrow of Drop down box,go to Battery Acid.
+
|-
−
Click on it.
+
||'''Slide Number 5'''
−
Notice that canter is filled with Battery acid to 1/2 L.
+
−
If we want more liquid click on red button of dropper and press it.
+
−
Click and drag probe.
+
−
Click on green prob and drag into canter liquid.
+
  
−
Point to pH meter.
+
'''Buffer Solutions'''
−
Observe the pH value.
+
||A '''buffer solution''',
−
Battery acid shows the pH=1.0
+
−
It is clear that Battery Acid is acidic solution.
+
is composed of a weak acid or weak base and its '''conjugate salt'''.
−
Click on water pump.
+
  
−
Point to pH meter.
+
Its pH changes very little when a small amount of acid or base is added to it.  
 +
|-
 +
||'''Slide Number 6'''
  
−
Cursor on pH meter.
+
'''Henderson–Hasselbalch Equation'''
−
Now click on the water pump to add more water that is 1L.
+
−
Observe the change in pH of solution with addition of more water.
+
−
Now pH meter shows the pH=1.51
+
−
Point to pH meter.
+
−
We can see that pH of Battery acid increases with addition of water.
+
  
−
This is because concentration of [H+] ion decreases which causing the acidity.
+
p<sup>H</sup> = pK<sub>a</sub>+ log {[A-] / [HA]}
 +
||'''Henderson–Hasselbalch''' equation is useful for estimating the pH of a buffer solution.
 +
|-
 +
||'''Slide Number 7'''
  
−
It is clear that with the dilution of acidic soultion -
+
'''Buffer Solutions-Tutorial'''
−
pH of acidic solution increases.
+
||Please refer to the excellent tutorial on buffers at the following link.
−
Acidity of acidic solution decreases and it aprroaches to neutral.
+
−
Click on Dropdown box arrow.
+
−
Go to and click hand soap.
+
−
Now click on black arrow of Dropdown box,go to hand soap and click on Hand Soap.
+
−
Point to pH meter.
+
−
For 1/2 L, pH meter shows the value of pH=10.0.
+
−
Click on water pump.
+
  
−
Point to pH meter.
+
http://chemcollective.org/activities/tutorials/buffers/buffers1
−
Click on water pump to add more water to hand soap.
+
|-
−
Notice the decrease in pH of Hand soap with addition of water.
+
||'''Slide Number 8'''
−
Cursor on pH meter.
+
−
For 1.04 L,Hand soap shows pH=9.66
+
−
we can see that pH of Hand soap decreases with dilution with water.
+
  
−
This is because concentration of [OH-] decreases with dilution.
+
'''Acetate Buffer Solution'''
  
−
It is clear that with the dilution of basic solution-
+
||To prepare '''Acetate buffer''' of a particular '''pH''',
−
pH of basic solution decreases
+
−
Basicity of basic solution decreases and it aprroaches to neutral.
+
−
Click on solution pump.
+
  
−
Click on Dropper.
+
'''Acetic acid''' and '''Sodium acetate''' are mixed in various proportions.
−
Point to pH meter.
+
−
Now click on lower solution pump to remove some hand soap solution.
+
−
Again click on dropper to add more hand soap.
+
−
We will see that again pH inceraes as concentration of [OH-]increases.  
+
  
−
Click on drop down box.
+
To prepare 50 ml of '''pH 3.6 Acetate buffer'''-
−
Cursor on spit.
+
−
point to pH meter.
+
−
Now ,we will check the pH of some liquids.
+
−
Click on black arrow of drop down box and select spit.
+
−
Meter shows the pH=7.40
+
−
Spit is basic liquid.
+
−
Click on dropdown box.
+
−
Cursor on milk
+
−
Point to pH meter.
+
−
Click on black arrow of dropdown box and select milk
+
−
Meter shows pH=6.50
+
−
It is clear that milk is acidic liquid.
+
−
Assignment
+
−
Assignment-
+
−
Check the pH for each liquid and arrange them in proper acidic and basic solutions.
+
−
Click on Micro screen.
+
−
Now,we will move to the Micro screen.
+
−
Click on Micro screen at the bottom of the interface.
+
  
 +
We have to mix 46.3 ml of  0.1 M '''Acetic acid''' and  3.7 ml of '''Sodium acetate'''.
 +
|-
 +
||Click on '''Workbench''' tab.
 +
||Back to the '''Workbench'''.
  
−
Point to pH scale.
+
Let us retrieve the chemicals and apparatus required for the experiment.
−
Point to concentration switch.
+
|-
 +
||From the '''Stockroom Explorer''' click on '''water''',  1M '''Sodium acetate''' and 1M '''Acetic acid'''.
  
−
Point to logarithmic switch.
+
||From the '''Stockroom Explorer''' click on '''water''',  1M '''Sodium acetate''' and 1M '''Acetic acid'''.
 +
|-
 +
||Click on '''Glassware''' icon.
  
−
Point to -ve red button.
+
Click on  '''Erlenmeyer flask''', select '''250 ml Erlenmeyer flask'''.
−
Left side of screen has the following tools-
+
  
−
pH scale at the left hand side of screen.
+
Click on '''Graduated cylinder'''.
−
Switch to select between concentration and quantity at the top of scale.
+
−
switch to select between logarithmic and linear scale at the bottom of scale.
+
−
-ve red button to hide pH scale.
+
  
 +
Click on  50 ml '''graduated cylinder'''.
 +
||From '''Glassware cabinet''' retrieve,
  
−
Point to Checkbox.
+
'''250 ml Erlenmeyer flask, 50 ml graduated cylinder'''.
 +
|-
 +
||Right-click on the '''graduated cylinder''', select duplicate.
  
−
Point to -ve red button.
+
Right-click on the '''graduated cylinder''' select rename.  
−
Right side of screen have the following tools-
+
−
Checkbox to select H30+/OH- ratio and molecule count.
+
−
-ve red button to hide pH.
+
−
Click on black arrow.
+
−
Go to and click on Soda Pop.
+
−
Now,click on black arrow of dropdown box to select liquid.
+
−
Go to drop down box and click on Soda Pop.
+
−
Point to pH meter
+
−
We will see that for 1/2 L pH meter shows Ph=2.50.
+
−
It means that Soda Pop is acidic solution.
+
  
−
Point to pH scale 3.2x10^-3
+
Rename as G1 and G2.
−
Point to pH scale 3.2 x 10^-12
+
||Make the duplicates of all the apparatus.
−
As Soda Pop is acidic we will see that-
+
−
Concentration of H30+ is high and OH- is low.
+
−
Click on quantity switch.
+
−
Point to H30+, OH- and H20.
+
  
−
If we click on quantity(mol),
+
Rename  '''graduated cylinders''' as G1 and G2.
−
we will see the number of moles of H30+(5.0X10^-3),OH-(5.0 x 10^-13) and H20(28).
+
|-
 +
||Right-click on the '''Erlenmeyer flasks''', select duplicate.
  
−
Click on linear.
+
Right-click on the '''Erlenmeyer flasks''', select rename.
−
Point to pH scale.
+
−
We can switch the logarithmic scale to linear.
+
−
click on linear .
+
−
We will see the pH scale in linear mode.
+
−
To bring the pH scale again in logarithmic mode, click on logarithmic mode.
+
−
Click on  H30+/OH- ratio check box.
+
−
Point to canter .
+
−
Now click on H30+/OH- ratio check box.
+
−
Canter contains large numbers of H30+ ions indicated by red dots.
+
−
Less number of Blue dot indicate number of OH- ion.
+
−
Click on molecule count check box.
+
  
−
point to 9.52 x 10^20
+
Rename as A1 and A2.
−
point to 3.79 x 10^12
+
||Rename '''Erlenmeyer flasks''' as A1 and A2.
−
point to 3.31 x 10^25
+
|-
−
To see the number of molecules in Soda Pop, click on molecule count check box.
+
||Cursor on the Workbench.
−
It will show number H30+, OH- and H20 molecules present in Soda Pop.
+
||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 water pump.
+
Click on Pour.
−
Point to H30+, OH- and H20.
+
  
 +
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.
  
−
Point to pH meter.
+
Pour the contents of the '''graduated cylinder G1''' into '''Erlenmeyer flask A1'''.
−
Now we will see how dilution affects the number of molecules.
+
|-
−
Click on water pump,fill the canter upto 1L.
+
||Place flask of water over graduated cylinder G1.
−
Observe the change in H30+/OH- ratio and molecule count.
+
Type 50 in the input bar for '''Precise Transfer mode'''.
−
Blue dots increases that means number of molecules of OH- increases.
+
−
PH is also increases, Ph meter shows the pH=2.80.
+
−
Assignment.
+
−
As an assignment ,
+
−
Measure the pH of blood sample.
+
−
Observe the change in molecule count and H30+/OH- ratio after dilution.
+
  
 +
Click on Pour.
  
−
Click on My Solution screen.
+
Bring the graduated cylinder over '''Erlenmeyer flask A1'''.
−
Now,we will move to the My Solution screen.
+
−
Click on My Solution screen at the bottom of the interface.
+
−
Point to My Solution screen.
+
−
My Solution screen has the same tool as that of Macro and Micro screen.
+
  
−
Point to Graduated Beaker.
+
Type 50 in the input bar for '''Precise transfer mode'''.
  
−
point to pH meter.
+
Click on '''Pour'''.
−
This screen has additional tool as-
+
||Measure 50 ml of water using the same '''graduated cylinder'''.
−
Graduated beaker at left hand side of screen.
+
  
−
PH meter to adjust pH directly.
+
Pour water into '''Erlenmeyer flask A1'''.
 +
|-
 +
||Click on flask A1.
  
−
Point to My Solution screen.
+
Point towards '''pH meter'''.
−
This screen allows directly manipulate pH or ion concentration.
+
||Click on flask A1 and note the '''pH'''.
  
 +
It shows a pH of  2.53.
 +
|-
 +
||Place 1M Sodium acetate flask over '''graduated cylinder G2'''.
  
−
Point to H30+and OH- slider.
+
Type 50 in the input bar for '''Precise Transfer mode'''.
−
point to Black Arrow.
+
−
In this screen we can make solution of our choice in two ways-
+
−
By moving the H30+and OH- slider
+
−
By pressing black arrow upward and downward.
+
−
Point to H30+and OH- slider.
+
−
Observe that H30+and OH- sliders moves simultaneously.
+
−
Point to pH meter.
+
−
Let's select pH 4.12 that is acidic solution for 1/2L.
+
−
Click on H30+and OH-ratio check box.
+
−
Click on molecule count check .
+
  
−
point to 2.29 x 10^19
+
Click on '''Pour'''.
 +
||Similarly prepare 0.5 M '''Sodium acetate''' solution.
  
−
point to 3.97 x 10^25
+
Measure 50 ml of 1M '''Sodium acetate''' solution in '''graduated cylinder G2'''.
−
Click on H30+and OH- ratio and molecule count check box.
+
|-
−
we will see that number of H30+molecules (red dots)large in number.
+
||Bring the graduated cylinder over '''Erlenmeyer flask A2'''.
−
OH- molecules (blue dots)small in number.
+
  
−
Point to  H30+ slider.
+
Type 50 in the input bar for '''Precise Transfer mode'''.
−
point to pH meter.
+
−
Now we will make basic solution.
+
−
move the H30+ slider downwards.
+
−
PH shows th value pH=11.81
+
  
 +
Click on '''Pour'''.
 +
||Transfer this solution into '''Erlenmeyer flask A2'''.
 +
|-
 +
||Place flask of water over '''graduated cylinder G2'''.
  
−
Point to 4.72 x 10^11
+
Type 50 in the input bar for '''Precise transfer mode'''.
  
−
point to 1.92 x 10^21
+
Click on '''Pour'''.
−
Now we will see that number of, H30+molecules (red dots)small in number.
+
−
OH- molecules (blue dots)large in number.
+
−
Point to 1.66 x 10^25
+
−
In both the cases the number of molecules of water remais the same.
+
  
−
Point to pH meter.
+
Bring the '''graduated cylinder''' over '''Erlenmeyer flask A2'''.
  
−
Point to 3.01 x 10^16
+
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 on 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 HCl and 1M NaOH to 0.1 M HCl and  0.1 M 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 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 NaOH  with water to prepare 0.1M NaOH.
 +
 
 +
 
 +
Prepare 0.1 M NaOH in '''beaker B''', similar 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 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 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 HCl  and 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.
 +
|-
 +
||'''Slide Number 11:'''
 +
 
 +
'''About Spoken Tutorial project'''
 +
||The video at the following link summarizes the Spoken Tutorial project.
  
−
Now we will make neutral solution.
 
−
Click on arrow to set the pH value=7.
 
−
In this case we will see that,
 
−
The number of H30+(Red dots) and OH- (blue dots) are  the same.
 
−
Slide
 
−
Assignment.
 
−
Assignment-
 
−
Make a solution of pH of your choice and  obseve the change in molecules.
 
−
Slide
 
−
Summery
 
−
In this simulation we have learn about
 
−
interactive PhET simulation,pH scale.
 
−
Slide
 
−
Summery
 
−
In this simulation we have learnt-
 
−
pH of solution
 
−
Determine the solution is acidic or basic on basis of pH
 
−
Place acids and bases in relative order.
 
−
Effect of dilution on pH of solution.
 
−
Logarithmic and linear scale.
 
−
Determine the concentarion of hydroxide, hydronium and water at a given pH
 
−
Slide Number13:
 
−
About Spoken Tutorial project
 
−
The video at the following link summarizes the Spoken Tutorial project.
 
 
Please download and watch it.
 
Please download and watch it.
−
Slide Number14:
+
|-
−
Spoken Tutorial workshops
+
||'''Slide Number 12:'''
−
The Spoken Tutorial Project team:
+
 
 +
'''Spoken Tutorial workshops'''
 +
||The Spoken Tutorial Project team:
 +
 
 
conducts workshops using spoken tutorials and
 
conducts workshops using spoken tutorials and
 +
 
gives certificates on passing online tests.
 
gives certificates on passing online tests.
 +
 
For more details, please write to us.
 
For more details, please write to us.
−
Slide Number 15:
+
|-
−
Forum for specific questions:
+
||'''Slide Number 13:'''
 +
 
 +
'''Forum for specific questions:'''
 +
 
 
Do you have questions in THIS Spoken Tutorial?
 
Do you have questions in THIS Spoken Tutorial?
 +
 
Please visit this site
 
Please visit this site
−
Choose the minute and second where you have the question.
+
 
 +
Choose the minute and second where you have the question
 +
 
 
Explain your question briefly
 
Explain your question briefly
−
Someone from our team will answer them.
+
 
−
Slide Number 16
+
Someone from our team will answer them
−
Forum for specific questions:
+
||Please post your timed queries in this forum.
−
The Spoken Tutorial forum is for specific questions on this tutorial
+
|-
−
Please do not post unrelated and general questions on them
+
||'''Slide Number 14:'''
−
This will help reduce the  clutter
+
 
−
With less clutter, we can use this discussions as instructional material.
+
−
Slide Number 17:
+
 
Acknowledgement
 
Acknowledgement
−
Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
+
||Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
−
More information on this mission is available at
+
 
−
this link.
+
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.
 +
|-
 +
|}

Revision as of 13:14, 20 June 2017

Time 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 0.1 M Acetic acid and 3.7 ml of 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 on 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 HCl and 1M NaOH to 0.1 M HCl and 0.1 M 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 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 NaOH with water to prepare 0.1M NaOH.


Prepare 0.1 M NaOH in beaker B, similar 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 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 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 HCl and 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.

Slide Number 11:

About Spoken Tutorial project

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

Please download and watch it.

Slide Number 12:

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 13:

Forum for specific questions:

Do you have questions in THIS Spoken Tutorial?

Please visit this site

Choose the minute and second where you have the question

Explain your question briefly

Someone from our team will answer them

Please post your timed queries in this forum.
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

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