View source for ChemCollective-Virtual-Labs/C3/Determination-of-Equilibrium-constant/English-timed

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|| '''Time''' 
|| '''Narration''' 

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|| 00:01
|| Welcome to this tutorial on '''Determination of Equilibrium Constant''' using '''Vlabs'''. 

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|| 00:08
|| In this tutorial, we will learn, To determine equilibrium constant for Cobalt chloride reaction. 

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|| 00:15
|| Observe the effect of change in temperature and concentration on equilibrium. 

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||00:22
||To follow this tutorial, you should be familiar with, '''ChemCollective Vlabs interface'''. 

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|| 00:29
|| If not for relevant tutorials please visit our website. 

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||00:34
|| Here I am using, 

'''Mac OS''' version 10.10.5 

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|| 00:39
|| '''ChemCollective virtual labs''' version 2.1.03 

'''Java''' version 8. 

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||00:48
||Here I have opened '''Vlabs''' interface. 

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||00:52
||Click on '''File''' menu. Scroll down to '''Load Homework''' option. 

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|| 00:57
|| '''Default Lab Setup''' dialog-box opens. 

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||01:02
||From the list, double-click on '''Chemical Equilibrium'''. 

Two options appear. 

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|| 01:10
|| Double-click on '''Cobalt Lab''' option. 

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||01:14
||'''Stockroom Explorer''' has required solutions and '''Problem Description'''. 

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||01:20
||Double-click on '''Problem Description'''. 

Problem description states that, we need to apply '''Le Chatelier's principle''', for aqueous '''Cobalt chloride''' reaction. 

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|| 01:33
||Using the equilibrium concentration we need to find, equilibrium constant for cobalt chloride reaction and 
 
Effect of temperature and reactant concentration on equilibrium. 

|- 
|| 01:47
||Let us define chemical equilibrium. 

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|| 01:50
|| '''Chemical equilibrium''' is a state of the reversible reaction when two opposing reactions occur at the same rate. 

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|| 01:59
||Concentration of the reactants and products do not change with time at equilibrium. 
 
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||02:06
|| This side shows a general '''Equilibrium Reaction'''. 

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|| 02:11
|| This is the equation for '''Equilibrium Constant'''. 

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|| 02:15
|| The chemical equation for this reaction is shown here. 

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|| 02:20
|| Cobalt forms complexes with water molecules, as well as chloride ions. 
 
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|| 02:27
|| A solution of '''Hexaaquacobalt(II)complex''' is pink. 

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|| 02:33
|| When hydrochloric acid is added to the solution, the colour changes to blue. 

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|| 02:39
|| This corresponds to the formation of '''Cobalt Chloride complex'''. 

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||02:44
|| Equilibrium Constant changes with, Change in concentration of reactants or products and 

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|| 02:51
|| Change in temperature. 

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||02:54
|| Click on '''Workbench'''. 

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|| 02:57
|| Double-click on '''Cobalt chloride experiment solutions''' cabinet. 

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|| 03:03
|| Double-Click on '''1M Cobalt Chloride.''' 

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|| 03:07
|| A flask with '''100 mL''' of '''1M Cobalt Chloride''' is added to the workbench. 

Observe the colour of the solution in the flask. 

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|| 03:18
|| '''Solution Info''' panel shows the required information. 

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|| 03:23
|| Colour of the solution is pink due to presence of '''Hexaaquacobalt(II)complex'''. 

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|| 03:30
||Note the concentrations of '''Hexaaquacobalt(II)complex''', '''chloride ions''' and '''Cobalt chloride''' in your observation book. 

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|| 03:40
|| Double-Click on '''12 M HydroCloric acid'''. 

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|| 03:44
|| Click on '''Glassware '''menu. Select '''Erlenmeyers'''. 

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|| 03:50
|| From the list click on 250 mL '''Erlenmeyer''' flask. 

Rename the flask as '''A'''. 

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|| 03:59
|| From the '''Glassware''' menu, select '''Pipets'''. 

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|| 04:03
|| From the list, click on 25 mL '''Pipet'''. 

From the '''Glassware''' menu, select 50 mL '''Buret'''. 

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|| 04:12
|| Using '''Pipet''', measure 25 mL of '''Cobalt chloride''' solution. 

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|| 04:18
|| Click on '''Withdraw'''. 

Keep the flask aside. 

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|| 04:23
|| Place the''' Pipet''' over '''flask A'''. 

Type '''25''' and Click on '''Pour'''. 

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|| 04:31
|| Keep the '''Pipet''' aside. 

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|| 04:34
|| Fill the '''buret''' with 50 ml of '''12 M hydrochloric acid'''. 

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|| 04:40
|| Bring '''12 M hydrochloric acid'''  flask on to 50 mL '''buret'''. 

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|| 04:46
|| Type 50 in the '''Transfer amount''' input bar. 

Click on '''Pour'''. 

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|| 04:52
|| Keep the flask aside. 

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|| 04:55
|| Bring the '''buret''' on to '''flask A'''. 

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|| 04:58
|| Add hydrochloric acid from the '''burette''' in 1 mL increments, using '''Precise Transfer''' mode. 

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|| 05:07
|| Type 1 in the '''Transfer amount''' input bar and click on '''Pour'''. 

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|| 05:13
|| Similarly transfer another 6 mL of hydrochloric acid using '''Precise Transfer''' mode. 

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|| 05:22
|| We have transferred 7 mL of hydrochloric acid to '''Flask A'''. 

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||05:28
|| Notice the change in temperature on the thermometer. 

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|| 05:33
|| Temperature decreases during the reaction. 

It means that, the reaction is '''endothermic'''. 

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|| 05:41
|| The total volume of solution in '''Flask A''' shows 32 mL. 

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|| 05:47
|| Observe the colour change in '''Flask A''', colour changes to brown. 

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|| 05:53
|| It may take a few seconds to reach equilibrium state. 

Now the concentrations of the reactants and products are constant. 

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|| 06:03
||Note the values of the concentrations of '''Hexaaquacobalt(II)complex''', '''chloride ions ''' and '''cobalt chloride '''  in your observation book. 

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|| 06:14
|| Continue the titration. 

Pour 1 mL at a time into the flask. 

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|| 06:21
||  Transfer another 8 mL of Hydrochloric acid to '''flask A'''. 

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|| 06:27
|| Now we have transferred 15 mL of hydrochloric acid to '''flask A'''. 

Total volume of liquid in '''flask A '''is 40 mL 

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|| 06:40
|| Note the colour change in '''Flask A'''. 

Please wait for the reaction to reach equilibrium condition. 

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||06:49
|| Again note the concentrations of '''Hexaaquacobalt(II)complex''', '''chloride ions''' and '''cobalt chloride''' in your observation book. 

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|| 07:00
|| Similarly add another 3 ml of hydrochloric acid to '''flask A'''. 

Total volume in '''flask A''' is 43 mL. 

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|| 07:11
|| Note the colour change in '''flask A'''. 

Note the concentrations in your observation book. 

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|| 07:19
|| Finally add 5 mL of hydrochloric acid''' from the ''' buret'''. 

Total volume in '''flask A''' is now 48 mL. 

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|| 07:30
|| Note that we have added 23 mL of hydrochloric acid to '''flask A'''. 

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|| 07:37
|| Colour of the solution in '''flask A''' is blue. 

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|| 07:41
|| Again note the concentrations of '''Hexaaquacobalt(II)complex''', '''chloride ions''' and '''cobalt chloride''' at equilibrium in your observation book. 

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|| 07:52
|| Let us see how to calculate '''Equilibrium Constant'''. 

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|| 07:56
|| Calculate '''Equilibrium Constant''' using the given formula. 

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|| 08:01
|| Substitute the values of concentrations of '''cobalt chloride''', '''Hexaaquacobalt(II)complex''' and '''chloride ions''' in the equation. 

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|| 08:11
|| This is the value of equilibrium constant after pouring 7 mL of  '''hydrochloric acid'''. 
 
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|| 08:19
|| Similarly, here are the values of equilibrium constant for 15, 18 and 23 mL of hydrochloric acid. 

|- 
|| 08:29
|| Since, temperature is constant, equilibrium constant  values are almost the same. 

|- 
|| 08:36
|| Switch to '''workbench'''. 

Next I will demonstrate the effect of temperature on equilibrium. 

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|| 08:45
|| Earlier we have observed that, this reaction is '''endothermic'''. 

It means, heat is absorbed during the reaction. 

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|| 08:54
|| '''Le Chatelier’s '''Principle states that, 

If an equilibrium is disturbed by changing the conditions, position of equilibrium moves to counteract the change. 

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|| 09:06
|| According to the principle, for endothermic reactions, rate of forward reaction increases with increase in temperature. 

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|| 09:14
|| Back to  '''workbench'''. Keep the burette aside. 

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||09:20
|| Let us increase the temperature of the reaction flask to '''35 degree Celcius.''' 

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|| 09:26
|| Right-click on flask '''A''', from the context menu, select '''Thermal Properties'''. 

Input box opens. 

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|| 09:35
|| In '''Set the temperature to''' text box, type '''35'''. 

Check the box for '''Insulated from surroundings'''. 

Click on '''OK'''. 

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|| 09:46
|| Thermometer shows '''35 degree Celcius.''' 

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||09:50
|| Note the values of concentrations of '''Hexaaquacobalt(II)complex''', '''Chloride ions''' and '''Cobalt Chloride'''. 

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||09:59
|| This is the calculated value of equilibrium constant at '''35 degree Celcius'''. 

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||10:05
|| Compare it to equilibrium constant value with that at '''25 degree Celcius'''. 

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|| 10:12
|| Note that the value of '''K<sub>c</sub>''' at '''35 degree Celcius ''' is greater than '''K<sup>c</sup> value''' at '''25 degree Celcius'''. 

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|| 10:21
|| This is because the reaction is an endothermic reaction. 

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|| 10:26
||As the temperature increases rate of forward reaction increases. 

Hence more product is formed. 

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|| 10:34
|| Switch to '''workbench''', 

Remove the used '''pipette''' and '''burette''' from the''' Workbench'''. 

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||10:42
|| Right-click on flask '''A''' 

From the context menu, select '''Thermal Properties'''. 

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|| 10:49
|| Un-check the box for '''Insulated from surroundings'''. 

Click '''OK'''. 

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|| 10:55
||This will bring the temperature back to 25 degree Celcius. 

|- 
|| 11:00
|| Now let us remove the chloride ions from the reaction using '''Silver Nitrate'''. 

|- 
|| 11:07
|| Double-Click on '''6M Silver nitrate''' from '''Stockroom Explorer'''. 

From the '''glassware''' menu, select 25 mL '''Pipet'''. 

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|| 11:18
|| Withdraw 25 mL of '''silver nitrate'''(AgNO<sub>3 </sub>) into the 25 mL '''Pipet'''. 

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|| 11:26
|| Transfer 25 mL of '''silver nitrate(AgNO<sub>3</sub>) from '''pipet''' to '''flask A''' in 5 mL increments. 
 
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|| 11:34
||Type 5 in '''Transfer Amount input bar'''. 

Click on Pour. 

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|| 11:40
|| Note the temperature. It increases as you add '''silver nitrate''' to flask A. 

|- 
|| 12:00
||Note the colour change. 

|- 
|| 12:02
|| It indicates the formation of '''Hexaaquacobalt(II)complex'''. 

Click on '''Solid''' radio button. 

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|| 12:11
||Note the amount of  '''silver chloride(AgCl)''' in '''grams''' column. 

|- 
|| 12:16
|| '''Silver nitrate(AgNO<sub>3</sub>)''' reacts with '''chloride(Cl<sup>-</sup>) ions in solution to form '''silver chloride(AgCl)'''. 

|- 
|| 12:23
|| Here chloride(Cl<sup>-</sup>) ions decrease in the solution, to compensate for the deficit, 
 
Rate of reverse reaction increases. 

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|| 12:33
|| Cobalt chloride complex decomposes to form '''HexaaquaCobalt(II)''' complex. 

This example is a proof for '''LeChatelier's''' principle. 

|- 
|| 12:44
|| Let us summarize. 

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||12:46
|| In this tutorial, we have learnt, To determine '''equilibrium constant''' for Cobalt chloride reaction. 

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|| 12:53
|| Observe the effect of change in temperature and concentration on equilibrium. 

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|| 12:59
|| As an assignment, 

Prepare a solution by adding 25 mL of Cobalt chloride solution and 23 mL of Hydrochloric acid. 

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|| 13:09
|| Add 40 mL of water in 10 mL increments to the prepared solution 

Observe the colour in the flask. 

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|| 13:19
|| Calculate Equilibrium Constant before and after addition of water. 

|- 
|| 13:25
|| The video at the following link summarizes the Spoken Tutorial project. 

Please download and watch it. 

|- 
|| 13:33
|| The '''Spoken Tutorial Project '''team, conducts workshops using spoken tutorials and 

gives certificates on passing online tests. 

For more details, please write to us. 

|- 
|| 13:45
|| Please post your timed queries on this forum. 

|- 
|| 13:49
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. 

More information on this mission is available at this link. 

|- 
|| 14:00
|| This tutorial is contributed by '''Snehalatha kaliappan ''' and '''Madhuri Ganapathi''' from '''IIT Bombay'''. 

Thank you for joining. 
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