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Determination of the Molar Heat of Fusion for Water and Heat of Solution of a Solid

Introduction to Thermochemistry & Heat:

1) Thermochemistry is one area of chemistry dealing with the quantitative analysis of heat absorbed or evolved by physical and chemical processes.

2) Heat (q) can be defined as the flow of energy into and out of a system due to a temperature difference between the thermodynamic system and its surroundings.

3) Heat energy will flow from the region of higher temperature to the region of lower temperature until thermal equilibrium has been reached.

a. At thermal equilibrium, the temperature of the two regions will be equal at any one time.

4) Heat & temperature are both measures of kinetic energy but?

a. Heat measures total energy.

b. Temperature measures the average energy.

c. Example to distinguish these two terms: If you had a teaspoonful of boiling water versus a cup of boiling water (both at 100oC), the cup of boiling water would be more painful to spill on your hand because it has more heat (total energy).

5) The formula for heat is as follows: q = s ( m ( ?t

a. q = heat, s = specific heat, m = mass, ?t = change in temperature.

i. Specific heat for water = 4.184 J/g ( oC.

Introduction to Heat of Fusion:

1) The heat needed to melt 1 mole of a pure substance is called the heat of fusion and denoted as ?Hfus.

2) To melt a pure substance at its melting point requires an extra boost of energy to overcome lattice energies.

3) The heat of fusion (?Hfus) can be calculated.

b. At constant pressure, the heat exchanged is equal to the heat of fusion:

i. qp = ?Hfus.

Introduction to Heat of Solution:

1) A solution is a homogeneous mixture of two or more substances, consisting of ions or molecules.

2) The solute is the dissolved substance for gases or solids in a liquid solution.

c. In other cases, it is the component that is in a smaller amount.

3) The solvent is the liquid substance in which the solids or gases are dissolved.

d. In other cases, it is the component that is in a larger amount.

4) When a solid dissolves in water, an energy change will always result.

e. Heat can be evolved or absorbed when an ionic compound dissolves in water.

5) The dissolving process occurs in two distinct steps:

f. The first step is the breaking down of the solid crystal lattice.

i. This process is endothermic (absorbing energy).

g. The second step is the hydration of the individual particles by the solvent.

i. This process is exothermic (releasing energy).

6) If the first step is dominant in the course of dissolving, then the process will be endothermic.

7) If the second step is dominant in the course of dissolving, then the process will be exothermic.

8) The heat of solution (?Hsol) can be calculated.

h. At constant pressure, the heat exchanged is equal to the heat of solution:

i. qp = ?Hsol

Substances to include in the Table of Chemical and Physical Properties:

Include the molar mass of the following substances ammonium nitrate, calcium chloride, and water.

Procedure for the Molar Heat of Fusion of Water:

1) Place about 400 ? 500 mL of deionized water into a 600 mL beaker and place onto a hotplate.

a. Heat up the water to between 60oC and 70oC.

2) Obtain the mass of two clean and dried empty Styrofoam cups with the top.

a. These two cups should be stacked on top of one another and the top should have a hole in it to facilitate the use of your thermometer.

3) Add enough warm water to the pre?weighed set of cups to fill between 65?75% full.

4) Obtain the mass of the set of cups containing the warm water with the cap on top.

a. Ensure that no water is clinging to the outside walls of the Styrofoam cups.

5) Measure the temperature of the warm water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC ? 0.01oC).

6) Immediately following this measurement, add enough ice to cover the surface of the water.

a. Ensure that you do not allow any of the warm water to splash out.

7) Replace the top and gently stir the mixture with the thermometer.

8) Once the ice has melted and the temperature has stabilized, record the final temperature of the cool water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC ? 0.01oC).

9) Following this measurement, remove the thermometer and record the mass of the cool water in the set of cups with the top.

10) Repeat this experiment (steps 1 ? 9) for a second trial.

Procedure for Heat of Solution of a Solid:

1) Obtain the mass of two clean and dried empty Styrofoam cups with the top.

2) Measure out approximately 10 ? 15 grams of solid ammonium nitrate. Record the mass.

3) Add between 150 ? 200 mL of deionized water to the Styrofoam cups.

4) Obtain the mass of the set of cups containing the water with the cap on top.

5) Measure the temperature of the water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC ? 0.01oC).

6) Immediately following this measurement, add the ammonium nitrate to the set of cups.

7) Replace the top and gently stir the mixture with the thermometer.

8) Once the solid has completely dissolved and the temperature has stabilized, record the final temperature of the cool water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC ? 0.01oC).

9) Following this measurement, rinse out and completely dry the set of cups.

10) Repeat this experiment with 10 ? 15 grams of anhydrous calcium chloride.

Clean ? Up:

1) All water and salt solutions can be disposed of down the sink.

Sample Data Table for the Molar Heat of Fusion of Water:

a) Mass of Styrofoam cups with top in grams:

Trial 1: ________ Trial 2: ________

b) Mass of Styrofoam cups with top plus warm water in grams:

Trial 1: ________ Trial 2: ________

c) Mass of warm water in grams (b ? a):

Trial 1: ________ Trial 2: ________

d) Stable temperature of warm water in oC:

Trial 1: ________ Trial 2: ________

e) Stable temperature of warm water in Kelvin:

Trial 1: ________ Trial 2: ________

f) Stable temperature of cool water in oC:

Trial 1: ________ Trial 2: ________

g) Stable temperature of cool water in Kelvin:

Trial 1: ________ Trial 2: ________

h) Temperature change of warm water in oC (f ? d):

Trial 1: ________ Trial 2: ________

i) Mass of Styrofoam cups with top plus cool water in grams:

Trial 1: ________ Trial 2: ________

j) Mass of cool water in grams (i ? a):

Trial 1: ________ Trial 2: ________

k) Mass of ice in grams (j ? c):

Trial 1: ________ Trial 2: ________

l) Amount of heat lost (in Joules) by the warm water?:

Trial 1: ________ Trial 2: ________

m) Amount of heat gained (in Joules) by the ice?:

Trial 1: ________ Trial 2: ________

n) Amount of heat (in Joules) that melted ice (???????????|l| ? |m|):

Trial 1: ________ Trial 2: ________

o) Experimental heat of fusion (in Joules/gram) of water (n/k):

Trial 1: ________ Trial 2: ________

p) Experimental molar heat of fusion (in Joules/mole) of water (o?Mm):

Trial 1: ________ Trial 2: ________

q) Experimental molar heat of fusion (in kilojoules/mole) of water (p/1000):

Trial 1: ________ Trial 2: ________
Average: ________

r) True molar heat of fusion (in kilojoules/mole) of water *: _____________

s) Percent error for molar heat of fusion of water: _____________

Sample Data Table for Heat of Solution of NH4NO3:

a) Mass of Styrofoam cups with top in grams: _____________

b) Mass of NH4NO3 in grams: _____________

c) Mass of Styrofoam cups with top plus water in grams: _____________

d) Mass of water in grams (c ? a): _____________

e) Stable temperature of water in oC: _____________

f) Stable temperature of in Kelvin: _____________

g) Stable temperature of water after solid addition in oC: ____________

h) Stable temperature of water after solid addition in Kelvin: ____________

i) Temperature difference in oC (g ? e): _____________

j) Temperature difference in Kelvin (h ? f): _____________

k) Amount of heat lost or gained (in Joules) by the water?: _____________

?q = (b+d)( 4.184 J/g ( oC)(i)

l) Amount of heat lost or gained (in Joules) by NH4NO3??: _____________

??qH2O = ?qNH4NO3

m) Number of moles of NH4NO3 used (b/Mm): _____________

n) Experimental heat of solution (in J/mol) of NH4NO3 (l/m): ____________

o) Experimental heat of solution (in kJ/mol) of NH4NO3(n/1000):_________

p) True heat of solution (in kJ/mol) of NH4NO3*: _____________

q) Percent error for heat of solution of NH4NO3: _____________

Sample Data Table for Heat of Solution of CaCl2:

a) Mass of Styrofoam cups with top in grams: _____________

b) Mass of anhydrous CaCl2 in grams: _____________

c) Mass of Styrofoam cups with top plus water in grams: _____________

d) Mass of water in grams (c ? a): _____________

e) Stable temperature of water in oC: _____________

f) Stable temperature of in Kelvin: _____________

g) Stable temperature of water after solid addition in oC: ____________

h) Stable temperature of water after solid addition in Kelvin: ____________

i) Temperature difference in oC (g ? e): _____________

j) Temperature difference in Kelvin (h ? f): _____________

k) Amount of heat lost or gained (in Joules) by the water?: _____________

?q = (b+d)(4.184 J/g ( oC)(i)

l) Amount of heat lost or gained (in Joules) by CaCl2??: _____________

??qH2O = ?qCaCl2

m) Number of moles of CaCl2 used (b/Mm): _____________

n) Experimental heat of solution (in J/mol) of CaCl2 (l/m): ____________

o) Experimental heat of solution (in kJ/mol) of CaCl2 (n/1000):_________

p) True heat of solution (in kJ/mol) of CaCl2*: _____________

q) Percent error for heat of solution of CaCl2: _____________

Barnett & Jones

General Chemistry-I Lab

?q = (c)(4.184 J/g ( oC)(h)

?q = (k)(4.184 J/g ( oC)(f?0.00oC)

PAGE

7

General Chemistry ? I Lab

Barnett

Pre-lab 4

Title: Periodic Trends

Date: 9/12/18

Unknown: N/A

Purpose: The purpose is to observe chemical properties of elements in periods (rows) and in

groups/families (columns).

Balanced Equations:

Part 1: Chemical Properties of the Alkaline Earth Metal Nitrates

Mg(NO3)2(aq) + Na2CO3(aq) ? MgCO3(s) + 2NaNO3(aq)

Ca(NO3)2(aq) + Na2CO3(aq) ? CaCO3(s) + 2NaNO3(aq)

Ba(NO3)2(aq) + Na2CO3(aq) ? BaCO3(s) + 2NaNO3(aq)

Part 2: Chemical Properties of the Halides

NaCl(aq) + AgNO3(aq) ? AgCl(s) + NaNO3(aq)

NaBr(aq) + AgNO3(aq) ? AgBr(s) + NaNO3(aq)

NaI(aq) + AgNO3(aq) ? AgI(s) + NaNO3(aq)

Part 3: Reactivity of Third Period Elements with Oxygen

2 Mg(s) + O2(g) ? 2 MgO(s)

4 Al(s) + 3 O2(g) ? 2 Al2O3(s)

Si(s) + O2(g) ? SiO2(s)

Part 4: Reactivity of Third Period Elements with Hydrochloric Acid

Mg(s) + 2 HCl(aq) ? MgCl2(aq) + H2(g)

2 Al(s) + 6 HCl(aq) ? 2 AlCl3(aq) + 3 H2(g)

Si(s) + 4 HCl(aq) ? SiCl4(aq) + 2 H2(g)

Table of Chemical and Physical Properties:

Chemical Name Molecular

Weight

Boiling Point Density Safety

Barium nitrate

Ba(NO3)2

261.34

529? C 3.24 g/cm

3 Poisonous. Do

not mix with

flammable

materials.

Silver nitrate

AgNO3

169.87 440? C 4.35 g/cm
3 Corrosive and

toxic. Avoid

skin contact.

Sodium Chloride

NaCl

58.44 801? C (melting

point)

2.16 g/cm3 Nonhazardous

Magnesium

Mg

24.31 650? C (melting

point)

1.738 g/cm3 Flammable. Do

not stare are

flame during

reaction with

magnesium and

oxygen

Calcium

Ca

40.08 842? C (melting

point)

1.54 g/cm3 Flammable

gases produced

with in contact

with water

Aluminum

Al

26.98 2460? C 2.7 g/cm
3 Flammable

Silicon

Si

28.09 2355? C 2.33 g/ml Nonhazardous

Oxygen

O

15.999 u 90.188 K 1.429 g/L Flammable gas

Hydrochloric

acid

HCl

36.46 110? C 1.18 g/cm
3 Toxic and

corrosive. Can

cause irritation

or burns to skin.

Procedure Observation

Part 1

1. Add 1ml of each solution to each
labeled test tubes

2. Add about three drops of solution
from tube 4 into tubes 1-3 and record

observations.

Part 2

3. Repeat steps 1&2 for part 2 with
different solutions

Part 3

4. On a watch glass, add small pieces of
magnesium, aluminum and silicon and

observe physical appearances.

5. Take turns placing each substance
over an open flame and record

observations.

Part 4

6. Place a small piece of magnesium,
aluminum, and silicon in separate test

tubes and label appropriately.

7. Place 1ml of HCl into each test tube
and record observations.

Data Collected:

Part 1

Aqueous

substances

Observations after reacting with 0.02 M Na2CO3

Mg(NO3)2

Ca(NO3)2

Ba(NO3)2

Part 2

Aqueous

substances

Observations after reacting with 0.10 M AgNO3

NaCl

NaBr

NaI

Part 3

Metallic

substances

Observations during and after reaction with atmospheric O2

Mg

Al

Si

Part 4

Metallic

substances

Observations during and after reaction with aqueous HCl

Mg

Al

Si

Discussion:

Conclusion:

Date Completed & Signature:

Banerjee

The lab notebook guidelines are included in this document.

1. Each lab period, in addition to coming to lab properly dressed, a pre-lab must be

prepared for the lab you are scheduled to perform that day. Failure to come to lab

without a complete pre-lab and improper dress will result in dismissal from the week?s

lab with a zero point allocation.

a. Each pre-lab should include the following sections: Name, Title, Date, Unknown,

Purpose, Balanced Equations, Table of Chemical and Physical Properties,

Procedure and an incomplete data table under Data Collected. This should be

uploaded on CANVAS before the start of lab and will be scanned for plagiarism.

This is due at the beginning of the lab period (mandatory).

2. Do not leave without checking out with your professor. You are allowed to use any

notebook or electronic notebook for this lab. Binded lab notebook is not needed for this

lab.

3. Lab reports (post-lab) are due 1 week following the completion of a lab. Each lab is

worth 100 points, comprising of pre and post lab. Your professor will provide further

instructions for completing your lab report.

a. Reports that are suspected to be plagiarized will be reported to the Dean, as

potential violators of the Academic Dishonesty guidelines (procedure 5026). This

will result in an F in the class. Self-plagiarism is also considered plagiarism.

4. The final lab report (post-lab) should comprise of 1) pre-lab sections, 2) Data collected,

3) Observations, 4) Discussion and 5) Conclusion and should be uploaded to CANVAS

placeholder.

Please upload at correct placeholder for each lab. Resubmissions are not allowed.

Please keep an eye on similarity score after submission.

Banerjee

Laboratory Notebook Guidelines

A proper laboratory notebook is one from which a given laboratory experiment can be repeated

by another chemist. Another chemist, chemical engineer or chemical patent lawyer should be

able to read your notebook and understand what you did and the results you obtained.

1. Every experiment should include the following sections listed below.

Title

Name

Date

Unknown (if any)

Purpose Describe the goal of the experiment.

Balanced Equation(s) (if any)

Table of Chemical and Physical Properties (including reference information, if

necessary)

Procedure & Do not provide a detailed, step-by-step procedure. The procedure is in

numerical form and should give the reader a general description of the procedure and any

special experimental details.

Observations . Throughout the lab, be sure to include any relevant observations: What

mass or volume did YOU use? Was the product a solid, liquid, gel, red precipitate, green

solution, etc?

Data Collected A sample data table is provided in each lab write-up. Record the

quantities of materials you used in the experiment. This includes calculations using

formulas, percent yield, percent error, etc.

Discussion Discussion should correlate expected data with obtained data in scientific

terms, without personal opinion.

Conclusion Conclusion should scientifically critic the success of the experiment, without

personal opinion and without over emphasis on errors.

The following sections must be completed prior to lab in the form of PRE-lab and uploaded to

CANVAS in correct placeholder: Name, Title, Date, Unknown, Purpose, Balanced Equations,

Table of Chemical and Physical Properties, Procedure and an incomplete data table under Data

Collected.

** All post-labs are due at the beginning of the next lab period on CANVAS, unless otherwise

specified. Each lab write-up is worth 100 points, including pre and post lab.

Banerjee

Lab reports must be written independently of lab partners,

students in other lab sections, and previous semesters?

students. Reports that are suspected to be plagiarized from any

of the previous sources will be submitted to the Dean, as

potential violators of the Academic Dishonesty guidelines

(procedure 5026). This will result in an F in the class.

THE FOLLOWING PAGE HAS A TEMPLATE ATTACHED FOR YOUR

CONVENIENCE:

Banerjee

Pre-lab

Your Name:

Title:

Date:

Unknown: (if none, write N/A)

(skip one line)

Purpose: Describe the goal of the experiment. Your purpose should answer the
following: What are you doing? Why are you doing it? How are you going do it?

This should be in your own words.

(skip one line)

Balanced Equations: (if none, write N/A)

(skip one line)

Table of Chemical and Physical Properties: The chemicals and
physical/chemical properties listed in the lab should be included in the table.

All the information can obtained from sigmaaldrich dot com.

Example:

Chemical

Name

Molecular

Weight

(g/mol)

Boiling

Point

(?C)

Density Safety

zinc 65.35 907 7.14

g/cm3

irritant,

combustible

copper

nickel

lead

polypropylene

water

Information obtained from:

http://www.sciencelab.com/msds.php?msdsId=9925476

http://pslc.ws/macrog/pp.htm

Banerjee

Procedure
1. Obtain 50 mL H2O.
2. Tare graduated cylinder

on a balance.

3. Add a rubber stopper,
after recording size.

Observations:
Actual volume: xx mL

Color change:

Gas evolution:

Temperature change:

Data Collected: The provided data table can be pasted into this section or
rewritten for each lab. Include calculations for theoretical yield, actual yield,

percent yield, percent error, and any other calculations that were performed in the

completion of the data table.

(skip one line)

Discussion: Discussion should correlate expected data with obtained data in scientific terms,
without personal opinion.

Conclusion: Conclusion should scientifically critic the success of the experiment, without
personal opinion and without over emphasis on errors.

Contents of discussion and conclusion together should not exceed five scientifically written

sentences.

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