ChemCollective-Virtual-Labs/C3/Heat-of-Reaction/English

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Visual Cue Narration
Slide Number 1

Title Slide

Welcome to this spoken tutorial on Heat of Reaction using Vlabs.
Slide Number 2

Learning Objectives

In this tutorial, we will learn to,

Determine heat change for the neutralisation of Sodium hydroxide (NaOH) and Hydrochloric acid(HCl).

Calculate heat of reaction for three different reactions.

Slide Number 3

Reactions


Rx1: NaOH(s) +H2O(l) ->

Na+(aq) + OH-(aq)


Rx2: NaOH (s) + HCl (aq) ->

Na+(aq) + Cl-(aq)+H2O


Rx3: NaOH (aq) + HCl (aq) ->

Na+(aq) + Cl-(aq) +H2O(l)

The three reactions are shown here.
Slide Number 4

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 5

System Requirement

Here, I am using

Mac OS 10.10.5

ChemCollective Vlabs version 2.1.0

Java version 8.

Click on Vlabs folder and

double-click on vlabs.exe file.

I have opened a Virtual Chemistry lab application window.
Click on File->Load homework.


Default Lab setup dialog box opens.

Thermochemistry >> Heat of the reaction

Click on File and select Load homework option.


Default Lab setup dialog box opens.

In the box, select Thermochemistry.


Double click on Heats of the reaction- Hess’s Law option.

Click on Stockroom Explorer and select Problem Description option. Click on Problem Description in Stockroom Explorer.
Cursor on Problem Description.

Scroll down the page and highlight the words Procedure, Processing Data, discussion and Conclusion.

The Problem Descriptionhere states that,


we have to determine and compare heat of reaction for 3 different reactions.


Scroll down the page and read,


Procedure, Processing the data, Discussion and Conclusion

Slide Number 6

Hess’s Law


∆ rH = ∆ r H 1 + ∆ r H 2 + ∆ r H 3 ….

This experiment is an illustration of Hess's law.


Which states that,


total heat change during the complete course of a reaction is same,


whether the reaction is made in one step or in several steps.


Heat of reaction is also known as Standard enthalpy change.

delta rH = delta r H 1 + delta r H 2 + delta r H 3 ,etc.

Slide Number 7

Hess’s law


ΔH1 + ΔH3 = ΔH2


Rx1 + Rx3= Rx2


Rx1: NaOH(s) +H2O(l) ->

Na+(aq) + OH-(aq)


Rx3: NaOH(aq) + HCl(aq) ->

Na+(aq) + Cl-(aq) +H2O(l)



Rx2: NaOH (s) + HCl (aq) ->

Na+(aq) + Cl-(aq)+H2O

Sum of Heats of reactions for,

Rx1 and Rx3 must be equal to heat of reaction for Rx2.

Rx=reaction

Go back to Workbench Let us go back to Workbench.


We will begin the first reaction.

Let us select the required chemicals and apparatus for the reaction.

From the Stockroom Explorer,

Double-click on Distilled water .


Go to Solids

Double click on Sodium hydroxide icons.

From the Chemical Stockroom,

Double-click on Distilled water.


Click on Solids cabinet and double-click on Sodium hydroxide.

Close the cabinet.

Click on Glassware icon. Double-click on 50 mL Graduated Cylinder. From the glassware menu, we will select a 50 mL Graduated Cylinder and a Foam Cup.
Click on select tools icon, double-click on Scale. From the instrument menu, select Weighing Boat and a Scale.
Drag the distilled water tank over to Graduated Cylinder.


In the Transfer amount input bar, Type 50. Click on Pour.

Keep the distilled water aside.

Transfer 50 mL of Distilled water to the Graduated Cylinder.

In the Transfer amount input bar, type 50 and click on Pour.

Drag Weighing Boat and place it on the scale.

Click on TARE.

Weigh 1 gram of Sodium hydroxide using Weighing Boat.

Place the Weighing Boat on the Scale, click on TARE.

Drag Sodium hydroxide bottle over to Weighing Boat.

Type 1 in the Transfer amount input bar.

Click on Pour.


Drag the Weighing Boat containing Sodium hydroxide bottle over Foam Cup.

Type 1 in the transfer amount input bar.

Click on Pour.

Drag the Sodium hydroxide bottle over the weighing boat.

Type 1 in Transfer amount input bar and click on Pour .


Transfer Sodium hydroxide from Weighing Boat to Foam Cup.


Click on Pour.

Click on Foam Cup.

Click on Solid radio button in the Solutions info panel, to see the weight in grams column.

Click on Foam Cup.

In the Solution info panel,

Click on Solid radio button and observe the weight in grams column.

Click on the Graduated Cylinder.

Drag the Graduated Cylinder to the Foam Cup.

Type 50 in the Transfer bar.

Click on Pour.


T1 = 25 o C.


Click on the Graduated Cylinder and record its temperature.


Thermometer shows the temperature as 25 degrees Celsius.


Drag the Graduated Cylinder over to the Foam Cup.


Type 50 in the Transfer Amount input bar and click on Pour.

T2 = 30.29 o C. Click on Foam Cup.

Record the highest temperature on the thermometer.

Thermometer shows 30.29 degrees Celsius.

Observe the grams column. Observe the grams column, it shows zero.


This is because all the Sodium hydroxide has now dissolved in water.

Lets see how to calculate heat of the reaction.
Slide Number 8

Heat of Reaction (q)

Formula


q = m * s *∆T

m = mass of the reactants

s = specific heat of the product

∆T = change in temperature in the reaction.

Heat of reaction (q) is calculated using the formula.

q = m * s * ∆T

wherein 'm' is mass of the reactants,

's' is the specific heat of the product and

'∆T' is the change in temperature in the reaction.

Slide Number 9

Calculation of heat of reaction Rx1


q = m * s * ∆T

m = 50 ml water + 1 g NaOH

s = 4.2 KJ/g

∆T = (T1- T2) = (25-30.29) = -5.29

q = (50+1) * 4.2 * (-5.29)

q= -1133.12/1000= -1.133 KJ.

Heat energy calculation for this reaction is given here.
Slide Number 10

Calculation of heat of reaction Rx1

ΔH = q/moles of NaOH

Number of moles of NaOH is =1/40 = 0.025.

ΔH1 =-.133/0.025 = -45.32 KJ mol-1

ΔH1= -45.32 KJ mol-1

Calculation of Molar Heat energy (delta H) in KJ/mol is given here.


delta H for reaction 1(Rx1) Sodium hydroxide is -45.32 KJ mol-1

Click on Foam Cup and Graduated Cylinder.

Press delete.

Lets go back to workbench.

let us delete the used Graduated Cylinder and Foam Cup.

Double-click on glassware icon.

Double-click on 50 mL Graduated Cylinder and Foam Cup.

We will now move on to demonstrate second exothermic reaction.

From Glassware menu,

Take a new 50 mL Graduated Cylinder and a Foam Cup.

From the Chemical Stockroom,

Double-click on 0.5 M Hydrochloric acid from the Strong-acids cabinet.

From the Chemical Stockroom, select Strong-acids cabinet.

Double click to get 0.5 M Hydrochloric acid.

Close the Cabinet.

Drag the 0.5M Hydrochloric acid bottle over the Graduated Cylinder.

Type 50 in the Transfer bar.

Click on Pour.

Transfer 50 mL of Hydrochloric acid into the Graduated Cylinder.
Drag Weighing boat and place it on the Scale.

Click on TARE.


Drag Sodium hydroxide bottle over to Weighing Boat.

Type 1 in the Transfer amount input bar.

Click on Pour.

Weigh 1 gram of Sodium hydroxide using Weighing Boat.


Transfer Sodium hydroxide from Weighing Boat to Foam Cup.

Click on the Graduated Cylinder.

Highlight the temperature.


T1 = 25 o C


Drag the Graduated Cylinder over Foam Cup.

Type 50 in the Transfer bar.

Click on Pour.

Click on the Graduated Cylinder, record its temperature.


Pour the contents of the Graduated Cylinder into the Foam Cup.

Click on the Foam Cup.

Highlight the temperature.

T2 = 36.96 o C

Click on the Foam Cup.


Record the highest temperature on the thermometer.


Thermometer shows 36.96 o C.

Slide Number 11

Calculation of heat of reaction for Rx2


q = m * s * ∆T.


∆T = (T1- T2) = (25 - 36.96) = -11.96.


q = (50+1) * 4.2 * -11.96


q = -2561.83 Joules


q = -2561.83 /1000=-2.561 KJ

ΔH2 = -2.561/0.025 = -102.47 KJ mol-1

Calculation of Molar Heat energy (delta H) in KJ/mol is given here.

delta H for reaction 2(Rx2) is -102.47 KJ mol-1

Select Foam Cup and Graduated Cylinder, scale and 0.5M HCl and press delete Delete the used apparatus and chemicals from the Workbench.
Double-click on Glassware icon.

Double-click on 25 mL Graduated Cylinder and a Foam Cup.


Right click on 25mL Graduated Cylinder.

Select the Duplicate option.


From Glassware menu take a new 25 mL Graduated Cylinder and a Foam Cup

We need two Graduated Cylinders.


Use Duplicate option in the context menu to make two copies.

Drag both the the cylinders. Drag both the cylinders to a convenient place on the Workbench.
Right click on the Cylinder.

Use context menu to rename the cylinder as A and B .

Label the cylinders as A and B.
On Chemical Stockroom;

Double-click on Strong-acids cabinet.

Double-click on 1.0 M HCl.


Double-click on Strong-bases cabinet.

Double-click on 1.0 M NaOH.

From the Chemical Stockroom click on Strong-acids cabinet.


Double click on 1.0 M Hydrochloric acid.

Close the cabinet.


From the Strong-bases cabinet, double click on 1.0 M Sodium hydroxide.

Close the cabinet.

Place 1 M HCl over the Graduated Cylinder.

Type 25 in the Transfer bar.

Click on Pour.


Click on the Graduated Cylinder.

Drag the Graduated Cylinder to the Foam Cup.

Type 25 in the Transfer bar.

Click on Pour.


Click on the Graduated Cylinder.

Highlight the temperature.

T1= 25o C

Transfer 25 mL of Hydrochloric acid(HCl) into graduated cylinder A.

Pour the Hydrochloric acid(HCl) from graduated cylinder to Foam Cup.


Note the temperature on the thermometer.

Place 0.1 M NaOH over the Graduated Cylinder.

Type 25 in the transfer bar.

Click on Pour.

Measure 25 mL of Sodium hydroxide in Graduated Cylinder B.
Click on the Graduated Cylindero

Drag the Graduated Cylinder to the Foam Cup.

Type 25 in the Transfer bar.

Click on Pour.

Pour the measured Sodium hydroxide into the Foam Cup.
Click on the Foam Cup.

Highlight the temperature


T2 = 31.67 o C

Click on Foam Cup.

Allow the reaction to take place for a few seconds.

Record the highest temperature.


Thermometer shows 31.67 o C.

Slide Number 12

Calculation of heat of reaction for Rx3

q = m * s * ∆T


∆T = (T1- T2) = (25 – 31.67) = -6.67


q =(25+25) * 4.2 * (-6.67)


q= -1400.7 Joules


q = -1400.7 /1000 = -1.400 KJ

ΔH3 =-1.400/0.025 = -56.03 KJ mol-1

Calculation of Molar Heat energy for reaction three is given here.


delta H for reaction 3( Rx3) is -56.03 KJ mol-1

Slide Number 13

Analysis of Results


This experiment is an example for Hess's law.


ΔH1 + ΔH3 = ΔH2


ΔH1 + ΔH3= (-45.32 KJ mol-1 + -56.03 KJ mol-1 ) = -101.35 KJ mol-1


ΔH2 = -102.47 KJ mol-1

Let us now analyze the results.


The value of Sum of heats of reactions for Rx1 and Rx3 is -101.35 KJ mol-1

Rx=reaction


The value of heat of reaction for Rx2 is -102.47 KJ mol-1


Therefore this experiment illustrates Hess's law.

Let us summarize.
Slide Number 14

Summary

In this tutorial we have,


Determined heat change for neutralization of Sodium hydroxide

and Hydrochloric acid.


Calculated heat of reaction for 3 different reactions.

Slide Number 15

Assignment


q = m * s * ∆T

q = (50+4) x 4.2 x (-21.18) = 4803.62 Joules

ΔH = 4803.62 /1000 = 4.803


ΔH = 4.803/0.1 = 48.03 KJ mol-1

For the assignment,

Explain why the reactions are exothermic.


Repeat Rx1 using 4 g of Sodium hydroxide and

calculate the heat of reaction.


Compare its value with the reaction in which 1 g of Sodium hydroxide was used.


Slide Number 16

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Slide Number 17

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Slide Number 18

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Slide Number 19

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