# Heats of Transition, Heats of Reaction, Specific Heats, and Hess s Law

Save this PDF as:

Size: px
Start display at page:

Download "Heats of Transition, Heats of Reaction, Specific Heats, and Hess s Law"

## Transcription

1 Heats of Transition, Heats of Reaction, Specific Heats, and Hess s Law GOAL AND OVERVIEW A simple calorimeter will be made and calibrated. It will be used to determine the heat of fusion of ice, the specific heat of metals, and the heat of several chemical reactions. These heats of reaction will be used with Hess s law to determine another desired heat of reaction. Objectives of the Data Analysis understand calorimetry and the concepts and uses of heat transfer understand heat transfer processes understand a variety of heat-related topics, including specific heat and heat capacity, heat of fusion, and heat of a chemical reaction use Hess s Law to deduce an unknown heat of reaction SUGGESTED REVIEW AND EXTERNAL READING See reference section; textbook information on calorimetry and thermochemistry BACKGROUND The internal energy, E, of a system is not always a convenient property to work with when studying processes occurring at constant pressure. This would include many biological processes and chemical reactions done in lab. A more convenient property is the sum of the internal energy and pressure-volume work ( w sys = P V at constant P). This is called the enthalpy of the system and is given the symbol H. H E + pv (definition of enthalpy, H) (1) Enthalpy is simply a corrected energy that reflects the change in energy of the system while it is allowed to expand or contract against a constant pressure. For any process occurring at constant pressure, the change in the enthalpy, H, is the heat absorbed or released by the system. H H final H initial = q p = heat absorbed by system (constant p) (2) A system can be thought to contain enthalpy, just as it does energy. Some contributions to the enthalpy of a system include the following. 1 Thermal Enthalpy. The higher the system s temperature, the greater its enthalpy. This makes sense because it takes heat to raise the temperature of an object. c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 1

2 2 Phase Enthalpy. The liquid phase has higher enthalpy than the solid, and the vapor phase has higher enthalpy than the liquid. This also makes sense because it takes heat to melt a solid or to vaporize a liquid. 3 Chemical Enthalpy. Chemical bonds store energy. When a chemical reaction occurs, the chemical enthalpy of the reactants changes when they form products. i ii If the reaction is exothermic, the chemical enthalpy decreases as the reaction proceeds. If the reaction is endothermic, the chemical enthalpy increases as the reaction proceeds. Enthalpy changes are determined by measuring the amount of heat transferred during a physical or chemical process. The quantitative treatment of the above three kinds of enthalpy, are all based on use of Eq. 2. Temperature When there is a change in the temperature of the system, H is proportional to the temperature change, T final T initial = T. The proportionality constant is called the heat capacity, and is given the symbol C. H H final H initial = C(T final T initial ) = C T (temperature change) (3) Because it is the difference in temperature that determines H, either C or K temperatures will give the identical result. H of the system is also proportional to the amount of material. The heat energy required to raise the temperature of one gram of material is its specific heat capacity, c. If amount is expressed in moles, then the molar heat capacity C is used. C total m c per gram = n C per mole (4a) Therefore, the system s H is the product of the amount, the heat capacity (specific or molar), and the change in temperature. H = C total T = m c per gram T = n C per mole T (4b) If T of the system is positive, temperature increases, the system absorbs heat, and q (or H ) is positive. If T of the system is negative, temperature decreases, the system gives off heat to its surroundings, and q (or H ) is negative. Unit analysis will help you determine how to use the above equation. H (or q) must have an energy unit. Units for heat capacity are: c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 2

3 c : energy per gram per degree e.g., J/ C g C : energy per mole per degree e.g., J/ C mol C general energy per degree e.g., J/ C. Phase At a phase change, the temperature of the system is constant until the transition is complete. The amount of heat required is proportional to the amount or material present, and the H of the phase transition. The heat energy can also be expressed in terms of moles (heat per mole). H = m h per gram = n H per mole (phase change) (5) The value of H is positive (heat is absorbed) for melting, vaporization, and sublimation processes. It is negative for the reverse (freezing, condensation, and deposition). In this experiment, we will use h to represent the enthalpy change per gram. Chemical Reaction The chemical reactions studied here occur at a particular pressure and temperature. Each reaction has an associated enthalpy change that is called the heat or enthalpy of reaction that depends on the way the reaction is balanced. For example, H reaction for 2 H 2 O 2 H 2 + O 2 is twice that forh 2 O H / 2 O 2, and H reaction is the heat absorbed when 2 moles of water decompose to give two moles of hydrogen and one mole of oxygen. In general, the equation to calculate the heat change is similar to Eq. 5. H = m h per gram = n H per mole (reaction) (6) Calorimeter A calorimeter is an insulated vessel in which physical or chemical processes are performed while neglecting heat flow between the vessel and its surroundings. A process in which the heat flow, q, equals zero is called adiabatic. To a first approximation, the heat flow (+ or ) between calorimeter and the surroundings is zero, so H (or q) for the calorimeter and its contents will be zero. H calorimeter and contents = q total = 0 (master equation for calorimeters) (7) Example 1: Calorimeter Calibration A mass m 1 of water at temperature T 1 is placed in the calorimeter. Mass m 2 of water at T 2 is added. The calorimeter itself has a small heat capacity that must be accounted for in order to have reasonable precision. The calorimeter always contributes a term to the total enthalpy change. c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 3

4 H calorimeter = C calorimeter (T final T initial contents ) (8) Initially, the calorimeter is at the same temperature, T 1, as the water it contains. When heat flow stops, all of the water and the calorimeter have reached the same temperature T final (at thermal equilibrium). In this example, there are three quantities contributing to the total enthalpy change (which is assumed to be zero): the two amounts of water and the calorimeter. H total = 0 (9a) H 1 + H calorimeter + H 2 = 0 (9b) m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m 2 c water (T final T 2 ) = 0 (9c) Note that the initial temperatures are not the same, but everything shares a common final temperature. Eq. 5 was used for H 1 and H 2. Generally all but one quantity in calculations like that shown in Eqns 9a, 9b, and 9c are measured or known. The equation is then solved for the unknown value. Example 2: Specific Heat Determination Suppose a mass m 1 of water with specific heat c 1 is placed in the calorimeter at T 1. Then a mass m 2 of another substance, such as a metal, at T 2 and with specific heat c 2 is added. The equation is similar to that of Eqns 9a, 9b, and 9c except that the c s do not cancel in the last step. H total = 0 (10a) H 1 + H calorimeter + H 2 = 0 (10b) m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m 2 c 2 (T final T 2 ) = 0 (10c) Note again that the initial temperatures are not the same, but everything shares a common final temperature. Eq. 5 was used for H 1 and H 2. Again, usually all but one quantity are measured or known. The equation is then solved for the unknown value. In 1819, after analyzing the heat capacities of many solid elements, Dulong and Petit proposed this generalization known as the Law of Dulong and Petit: C per mole = MMc per gram = constant for all metals = 3R MM = molar mass of the metal; R = gas constant (8.314 J/k mol). (11) Using precise specific heat measurements, Berzelius used Eq. 11 to find many molar masses. In 1830, he published an extremely accurate table of molar masses that gave great impetus to the c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 4

5 development of atomic/molecular theory. Example 3: Enthalpy of Phase Change Determination Suppose a mass m 1 of water is placed in the calorimeter at T 1, and mass m 2 of ice at 0 C is added. As the apparatus reaches thermal equilibrium, several things occur. First, the ice melts, pulling its heat of fusion out of the thermal energy of the water and calorimeter, thus lowering their temperatures. Second, when the ice has melted, the resulting liquid is still at 0 C, so that water has to be further heated until it, the water it is cooling, and the calorimeter reach the same final temperature. H total = 0 (12a) H cool water + H cool calorimeter + H melt ice + H warm melted ice = 0 (12b) m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m ice h fusion, per g + m ice C water (T final 0 C) = 0 (12c) Note that the heat of fusion of ice is expressed in units of energy per mass (J/g or kj/g); if the amount of ice were in moles, the heat of fusion would have units of energy per mole (J/mol or kj/mol). Example 4: Reaction Enthalpy Determinations Suppose mass m 1 of a water-based solution is placed in the calorimeter at T 1. To that mass m 2 of a substance of molar mass M 2 is added and it reacts with the solution. If substance 2 is the limiting reactant, then all of it will react. The enthalpy change will depend on the heat of reaction and on the number of moles of substance 2 added, n 2 = m 2 /MM 2. In this case, there are three contributions to the total enthalpy change of zero. They are due to the temperature change of the water solution and calorimeter, plus the enthalpy change due to the chemical reaction. For reactions in solution, the heat capacities of the reactants and products are approximated as zero because only the water and the calorimeter have significant heat capacity. In the last step it is assumed that the chemical reaction is written in such a way that the stoichiometric coefficient on the reactant, substance 2, is 1. H total = 0 (13a) H 1 + H calorimeter + H chemical reaction = 0 (13b) m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m 2 MM 2 H reaction = 0 (13c) c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 5

6 The last term has been written so that H reaction has a unit of energy per mole (J/mol or kj/mol). In 1840, Hess stated that the evolution of heat by chemical reactions is the same, regardless of whether the reaction takes place in one step or in more than one. Heats of reaction are changes in the property, H, of a system. When a system changes from state 1 to state 2, H will have to change by the amount H 2 H 1, regardless of the number or kind of steps involved in the process. Hess Law permits the heats of experimentally difficult reactions to be deduced from measurements of other more convenient reactions. EXPERIMENTAL NOTES There are two possibilities for your calorimeter setup, but both require the same procedure. a b Coffee Cup Calorimeter Setup the calorimeter consists of two nested Styrofoam cups with a lid. Styrofoam Calorimeter Setup the calorimeter consists of a Styrofoam base and lid. Figure 1 A thermometer is placed through a hole in the lid to measure the temperature of the liquid. If you use set-up (a), use a slotted rubber stopper to protect the thermometer in the clamp. Both setups are constant pressure calorimeters. Please do not throw your calorimeter away. Return it clean to the reagent bench. this applies to both (a) and (b). Measurements The two key measurements for all calorimetry experiments are masses and temperature changes. Make sure you have all of the data you need to complete the lab. You may need these conversion factors: 1000 J = 1 kj, and J = 1 cal. Note: Make sure you record/obtain all information required to complete the calculations. This includes the heat capacity of all calorimeters used to gather your data. c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 6

9 4 Leave the test tube there for at least 30 minutes to equilibrate the metal to the temperature of the bath. Do this at the start of the experiment so the metal heats while you are doing other things. Keep the calorimeter away from the hot plates. CAUTION: Steam burns are especially severe, as the steam condenses to liquid on your skin and gives up its heat of vaporization to the tissues. So whenever you work around steam, pay attention. 5 Record the mass of the clean, dry calorimeter to 0.01 g. 6 Put about 100 ml of water into it and record the mass to 0.01g. 7 Record the temperature of the water and calorimeter to 0.1 C. 8 Carefully record the temperature of the boiling water bath with a 110 C thermometer (to 0.5 C). 9 Carefully slide the hot metal from the test tube into the calorimeter. Do not hit the thermometer or add boiling water from the bath. Do not let the thermometer touch the metal. 10 Swirl the calorimeter gently and constantly. 11 Record the maximum temperature to 0.1 C. 12 Return the clean, dry, cool metal to the reagent bench. 13 Calculate the specific heat of your metal to three significant figures, using Eqns. 10a, 10b, and 10c, in units of J/g and J/mol. H 1 + H calorimeter + H 2 = m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m 2 c 2 (T final T 2 ) = 0 (10d) 14 Using the molar mass and experimental specific heat of your metal, calculate the molar heat capacity, C, and compare it to the Dulong and Petit value of 3R (R = J/K mol). Part 4: Heat of a Chemical Reaction This experiment is discussed in Example 4. You will measure the heats of two reactions: a Mg + 2 HCl MgCl 2 + H 2 (g) H a = measured b MgO + 2 HCl MgCl 2 + H 2 O(l) H b = measured You also need a H value for reaction c, which is from the literature. c H 2 (g) + 1 / 2 O 2 (g) H 2 O(l) H c = kj Using these H values and Hess s Law, you can determine the H for magnesium combustion (or formation), where magnesium metal is burned in oxygen. c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 9

10 d Mg + 1 / 2 O 2 MgO H d =??? 1 Record the mass of the clean, dry calorimeter to 0.01 g. 2 Put 50 ml of distilled water into the calorimeter. 3 Add 25 ml of approximately 2 M HCl. 4 Record the mass of this water and acid combination to 0.01 g. 5 Take about g of magnesium ribbon and record its mass to 0.01 g. 6 Take the initial temperature of the acidic water in the calorimeter to 0.1 C. 7 Add the metal, stir constantly, and record the maximum temperature reached to 0.1 C. The reaction takes a while, so be patient. 8 Repeat this procedure substituting about 0.30g of magnesium oxide for the magnesium ribbon. The goal is to determine the heat of reaction for the combustion of magnesium to form the oxide. Target: Mg + 1 / 2 O 2 MgO H rxn =? 9 Using Eqns. 13a, 13b, and 13c, calculate the experimental values of H a and H b reactions (a) and (b) to three significant figures. H 1 + H calorimeter + H chemical reaction = m 1 c water (T final T 1 ) + C calorimeter (T final T 1 ) + m 2 MM 2 H reaction = 0 (13d) 10 Using H a, H b, and H c, employ Hess Law to calculate the heat of reaction for the magnesium combustion reaction (to three significant figures). Note: Whenever you reverse a reaction, the sign of H changes. That is because enthalpy is a state function; H of state 2 to state 1 is equal in magnitude but opposite in sign of H from state 1 to state Calculate the percent error in experimental value for the target reaction (literature value for the heat of formation of MgO(s) 601 kj) to three significant figures. 12 Calculate the percent error in your experimental H a and H b values (literature values are 462 kj/mol for (a) and 146 kj/mol for (b)) to three significant figures. Waste Disposal: As per TA instruction; you will lose points if you do not dispose of waste properly. REPORTING RESULTS Complete your lab summary or write a report (as instructed). Abstract c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 10

11 Results (final results are reported to three significant figures) Calorimeter heat capacity Heat of fusion of ice Specific heats of metals Heats of reaction from part 4 and for combustion of Mg. Sample Calculations Calorimeter heat capacity (part 1) Heat of fusion of ice (part 2) Specific heat of metals (part 3) Heat of reaction for one of part 4 reactions (part 4) Heat of magnesium combustion using Hess Law (part 4) Discussion What you found out and how for each part How good was your data (comparison to expected values, etc.) Ideas to improve the accuracy in any or all of the procedures utilized in this experiment? What conclusions can you draw? Review c 2011 Advanced Instructional Systems, Inc. and the University of California, Santa Cruz 11

### q = (mass) x (specific heat) x T = m c T (1)

Experiment: Heat Effects and Calorimetry Heat is a form of energy, sometimes called thermal energy, which can pass spontaneously from an object at a high temperature to an object at a lower temperature.

### Procedure. Day 1 - Calibration of the Calorimeter. (Part I) The Heat Capacity of the Calorimeter.

Thermochemistry Experiment 10 Thermochemistry is the study of the heat energy involved in chemical reactions and changes of physical state. Heat energy is always spontaneously transferred from hotter to

### Transfer of heat energy often occurs during chemical reactions. A reaction

Chemistry 111 Lab: Thermochemistry Page I-3 THERMOCHEMISTRY Heats of Reaction The Enthalpy of Formation of Magnesium Oxide Transfer of heat energy often occurs during chemical reactions. A reaction may

### 2 To use calorimetry results to calculate the specific heat of an unknown metal. 3 To determine heat of reaction ( H) from calorimetry measurements.

Calorimetry PURPOSE To determine if a Styrofoam cup calorimeter provides adequate insulation for heat transfer measurements, to identify an unknown metal by means of its heat capacity and to determine

### Prelab attached (p 8-9) (g)! MgO (s) + heat (1)

CHEM 151 ENTHALPY OF FORMATION OF MgO FALL 2008 Fill-in Prelab attached (p 8-9) Stamp Here Name Partner Lecture instructor Date INTRODUCTION Chemical reactions either produce heat as they proceed (exothermic)

### CALORIMETRY AND HESS LAW: FINDING H o FOR THE COMBUSTION OF MAGNESIUM

Experiment 12J FV 7/16/06 CALORIMETRY AND HESS LAW: FINDING H o FOR THE COMBUSTION OF MAGNESIUM MATERIALS: Styrofoam coffee cup and lid, thermometer, magnetic stirrer, magnetic stir bar, 50-mL and 100-

### THERMOCHEMISTRY & DEFINITIONS

THERMOCHEMISTRY & DEFINITIONS Thermochemistry is the study of the study of relationships between chemistry and energy. All chemical changes and many physical changes involve exchange of energy with the

### Calorimetry Experiments

Calorimetry Experiments Pre-Lab: Today s laboratory period will include a variety of activities designed to re-familiarize you with safe practices for chemistry laboratory, the space and equipment you

### Chapter 5 Thermochemistry

Chapter 5 Thermochemistry I. Nature of Energy Energy units SI unit is joule, J From E = 1/2 mv 2, 1J = 1kg. m 2 /s 2 Traditionally, we use the calorie as a unit of energy. 1 cal = 4.184J (exactly) The

### Experiment 14 - Heats of Reactions

Experiment 14 - Heats of Reactions If a chemical reaction is carried out inside a calorimeter, the heat evolved or absorbed by the reaction can be determined. A calorimeter is an insulated container, and

### Heat of Neutralization

Cautions HCl and NaOH are corrosive and toxic Purpose The purpose of this experiment is to determine the heat of neutralization for a reaction between a strong acid and a strong base. Introduction Chemical

### Thermochemistry: Enthalpy of Reaction Hess s Law

Thermochemistry: Enthalpy of Reaction Hess s Law Objective Demonstrate Hess s Law for determining the enthalpy of formation for MgO by measuring temperature change for several reactions. Introduction The

### DETERMINING THE ENTHALPY OF FORMATION OF CaCO 3

DETERMINING THE ENTHALPY OF FORMATION OF CaCO 3 Standard Enthalpy Change Standard Enthalpy Change for a reaction, symbolized as H 0 298, is defined as The enthalpy change when the molar quantities of reactants

### Thermochemistry: Calorimetry and Hess s Law

Thermochemistry: Calorimetry and Hess s Law Some chemical reactions are endothermic and proceed with absorption of heat while others are exothermic and proceed with an evolution of heat. The magnitude

### Calorimetry: Determining the Heat of Fusion of Ice and the Heat of Vaporization of Liquid Nitrogen - Chemistry I Acc

Calorimetry: Determining the Heat of Fusion of Ice and the Heat of Vaporization of Liquid Nitrogen - Chemistry I Acc O B J E C T I V E 1. Using a simple calorimeter, Determine the heat of fusion of ice

### By adding Equations 1, 2, and 3, the Overall Equation is obtained. Summation of their enthalpies gives the enthalpy of formation for MgO.

The standard enthalpy of formation of a compound, Hf o, is the heat change accompanying the formation of one mole of compound from the elements at standard state. The standard state of a substance is the

### HEATS OF REACTION. Name: Chemistry 117 Laboratory University of Massachusetts Boston LEARNING GOALS

Name: Chemistry 117 Laboratory University of Massachusetts Boston HEATS OF REACTION LEARNING GOALS 1. Become familiar the technique of calorimetry to measure heats of reaction 2. Become familiar with the

### Experiment 6 Coffee-cup Calorimetry

6-1 Experiment 6 Coffee-cup Calorimetry Introduction: Chemical reactions involve the release or consumption of energy, usually in the form of heat. Heat is measured in the energy units, Joules (J), defined

### Bomb Calorimetry. Example 4. Energy and Enthalpy

Bomb Calorimetry constant volume often used for combustion reactions heat released by reaction is absorbed by calorimeter contents need heat capacity of calorimeter q cal = q rxn = q bomb + q water Example

### Explorations in Thermodynamics: Calorimetry, Enthalpy & Heats of Reaction

Explorations in Thermodynamics: Calorimetry, Enthalpy & Heats of Reaction Dena K. Leggett, Ph.D. and Jon H. Hardesty, Ph.D. Collin County Community College Dept. of Chemistry 1. Introduction: One of the

### Experiment 7: Enthalpy of Formation of Magnesium Oxide

Experiment 7: Enthalpy of Formation of Magnesium Oxide Objective: In this experiment, a simple calorimeter will be constructed and calibrated, and Hess' law of constant heat summation will be used to determine

### Lab Session 9, Experiment 8: Calorimetry, Heat of Reaction

Lab Session 9, Experiment 8: Calorimetry, Heat of Reaction Specific heat is an intensive property of a single phase (solid, liquid or gas) sample that describes how the temperature of the sample changes

### EXPERIMENT 9. Thermochemistry: Hess Law and the Heat of Formation of MgO

Outcomes EXPERIMENT 9 Thermochemistry: Hess Law and the Heat of Formation of MgO After completing this experiment, the student should be able to: 1. Differentiate between exothermic and endothermic reactions.

### CHM111 Lab Enthalpy of Hydration of Sodium Acetate Grading Rubric

Name Team Name CHM111 Lab Enthalpy of Hydration of Sodium Acetate Grading Rubric Criteria Points possible Points earned Lab Performance Printed lab handout and rubric was brought to lab 3 Safety and proper

### Energy Changes in Chemical Reactions. System loses heat (negative); gains heat (positive) Describe the difference between the two.

Energy Changes in Chemical Reactions Most reactions give off or absorb energy Energy is the capacity to do work or supply heat. Heat: transfer of thermal (kinetic) energy between two systems at different

### CHEMISTRY Practice exam #4 answer key October 16, 2007

CHEMISTRY 123-01 Practice exam #4 answer key October 16, 2007 1. An endothermic reaction causes the surroundings to a. warm up. b. become acidic. c. condense. 2. Which of the following is an example of

### Chapter Six. Energy Relationships in Chemical Reactions

Chapter Six Energy Relationships in Chemical Reactions 1 Energy (U): Capacity to Do Work Radiant energy Energy from the sun Nuclear energy Energy stored in the nucleus of an atom Thermal energy Energy

### The Relationships Between. Internal Energy, Heat, Enthalpy, and Calorimetry

The Relationships Between Internal Energy, Heat, Enthalpy, and Calorimetry Recap of Last Class Last class, we began our discussion about energy changes that accompany chemical reactions Chapter 5 discusses:

### Example: orange juice from frozen concentrate.

Dilution: a process in which the concentration (molarity) of a solution is lowered. The amount of solute (atoms, moles, grams, etc.) remains the same, but the volume is increased by adding more solvent.

### Name: Thermochemistry. Practice Test A. General Chemistry Honors Chemistry

Name: Thermochemistry Practice Test A General Chemistry Honors Chemistry 1 Objective 1: Use the relationship between mass, specific heat, and temperature change to calculate the heat flow during a chemical

### Name Date Class THERMOCHEMISTRY. SECTION 17.1 THE FLOW OF ENERGY HEAT AND WORK (pages 505 510)

17 THERMOCHEMISTRY SECTION 17.1 THE FLOW OF ENERGY HEAT AND WORK (pages 505 510) This section explains the relationship between energy and heat, and distinguishes between heat capacity and specific heat.

### Name: Thermochemistry. Practice Test B. General Chemistry Honors Chemistry

Name: Thermochemistry B Practice Test B General Chemistry Honors Chemistry 1 Objective 1: Use the relationship between mass, specific heat, and temperature change to calculate the heat flow during a chemical

### Thermochemistry. Chapter 6. Concept Check 6.1. Concept Check 6.2. Solution

Chapter 6 Thermochemistry Concept Check 6.1 A solar-powered water pump has photovoltaic cells on protruding top panels. These cells collect energy from sunlight, storing it momentarily in a battery, which

### Lab 9. Hess s Law. Reaction B. NaOH (s) + HCl (aq) NaCl (aq) + H 2 O (l) Reaction C. NaOH (aq) + HCl (aq) NaCl (aq) + H 2 O (l)

Lab 9. Hess s Law Prelab Assignment Before coming to lab: This exercise does not require a report in your lab notebook. Use a pen to record your data, observations, calculations and analysis in the spaces

### Calorimetry and Enthalpy. Chapter 5.2

Calorimetry and Enthalpy Chapter 5.2 Heat Capacity Specific heat capacity (c) is the quantity of thermal energy required to raise the temperature of 1g of a substance by 1⁰C The units for specific heat

### L q + w. CHM 1041 Thermochemistry Heats of Solution (Reaction) J. Bieber. Section: Date:

CHM 1041 Thermochemistry Heats of Solution (Reaction) J. Bieber Name: Partner: Section: Date: To study quantitatively the heat of solution when (1) a salt dissolves in water and (2) to study the heats

### EXPERIMENT 12N CALORIMETRY

EXPERIMENT 12N CALORIMETRY FV 7/28/2016 MATERIALS: PURPOSE: OBJECTIVES: Styrofoam cup and lid, stir bar, magnetic stir plate, digital thermometer, 250 ml beaker, two 100 ml graduated cylinders, aluminum

### Heats of Reaction lab. Enthalpy

Heats of Reaction lab tonight s QuestiONs Is the amount of heat given off or absorbed, q sys, by a chemical reaction an intensive or extensive property? For an acid-base reaction, does the heat of reaction

### Enthalpy of Neutralization. Introduction

Enthalpy of Neutralization Introduction Energy changes always accompany chemical reactions. If energy, in the form of heat, is liberated the reaction is exothermic and if energy is absorbed the reaction

### Chapter 5. Thermochemistry

Chapter 5. Thermochemistry THERMODYNAMICS - study of energy and its transformations Thermochemistry - study of energy changes associated with chemical reactions Energy - capacity to do work or to transfer

### Experiment 9: Enthalpy of Formation of Magnesium Oxide

1 Experiment 9: Enthalpy of Formation of Magnesium Oxide Objective: In this experiment, a simple calorimeter will be constructed and calibrated, and Hess law of constant heat summation will be used to

### Chemistry 1215 Make up Lab Enthalpy of Neutralization

hemistry 1215 Make up Lab Enthalpy of Neutralization Objective In this experiment you will determine the molar enthalpy of neutralization of an acid. Introduction The study of energy and its transformations

### ENERGY. Thermochemistry. Heat. Temperature & Heat. Thermometers & Temperature. Temperature & Heat. Energy is the capacity to do work.

ENERGY Thermochemistry Energy is the capacity to do work. Chapter 6 Kinetic Energy thermal, mechanical, electrical, sound Potential Energy chemical, gravitational, electrostatic Heat Heat, or thermal energy,

### Thermodynamics. Energy can be used * to provide heat * for mechanical work * to produce electric work * to sustain life

Thermodynamics Energy can be used * to provide heat * for mechanical work * to produce electric work * to sustain life Thermodynamics is the study of the transformation of energy into heat and for doing

### Instruction Manual and Experiment Guide F. Basic Calorimetry Set TD-8557A

Instruction Manual and Experiment Guide 012-03060F Basic Calorimetry Set TD-8557A Al Cu W Table of Contents Introduction......................................................................... 1 Notes

### Thermochemistry I: Endothermic & Exothermic Reactions

THERMOCHEMISTRY I 77 Thermochemistry I: Endothermic & Exothermic Reactions OBJECTIVES: Learn elementary concepts of calorimetry and thermochemistry Practice techniques of careful temperature, mass, and

### Determination of the Molar Mass of an Unknown Solid by Freezing Point Depression

Determination of the Molar Mass of an Unknown Solid by Freezing Point Depression GOAL AND OVERVIEW In the first part of the lab, a series of solutions will be made in order to determine the freezing point

### CHAPTER 6 THERMOCHEMISTRY

Chapter 6 Thermochemistry Page 1 CHAPTER 6 THERMOCHEMISTRY 6-1. The standard state of an element or compound is determined at a pressure of and a temperature of. (a) 760 atm, 0 o C (b) 1 mmhg, 273 o C

### Calorimetry - Specific Heat and Latent Heat

Chapter 3 Calorimetry - Specific Heat and Latent Heat Name: Lab Partner: Section: 3.1 Purpose The purpose of this experiment is to study the relationship between heat and temperature. Calorimetry will

Thermochemistry Reading: Chapter 5 (omit 5.8) As you read ask yourself What is meant by the terms system and surroundings? How are they related to each other? How does energy get transferred between them?

### 3. Of energy, work, enthalpy, and heat, how many are state functions? a) 0 b) 1 c) 2 d) 3 e) 4 ANS: c) 2 PAGE: 6.1, 6.2

1. A gas absorbs 0.0 J of heat and then performs 15.2 J of work. The change in internal energy of the gas is a) 24.8 J b) 14.8 J c) 55.2 J d) 15.2 J ANS: d) 15.2 J PAGE: 6.1 2. Calculate the work for the

### Determination of the Empirical Formula of Magnesium Oxide

Determination of the Empirical Formula of Magnesium Oxide GOAL AND OVERVIEW The quantitative stoichiometric relationships governing mass and amount will be studied using the combustion reaction of magnesium

### 7 THERMOCHEMISTRY: HEAT OF REACTION

7 THERMOCHEMISTRY: HEAT OF REACTION Name: Date: Section: Objectives Measure the enthalpy of reaction for the decomposition of hydrogen peroxide Measure the heat capacity of a Styrofoam cup calorimeter

### Enthalpy changes and calorimetry. Enthalpy changes in reactions Calorimetry and heat measurement Hess s Law Heats of formation

Enthalpy changes and calorimetry Enthalpy changes in reactions Calorimetry and heat measurement Hess s Law Heats of formation Learning objectives Describe the standard state for thermodynamic functions

### Chapter 16 Review Packet

Chapter 16 Review Packet AP Chemistry Chapter 16 Practice Multiple Choice Portion 1. For which process is ΔS negative? Note: ΔS = S final S initial therefore, if ΔS is positive, S final > S initial if

### AP* Chemistry THERMOCHEMISTRY

AP* Chemistry THERMOCHEMISTRY Terms for you to learn that will make this unit understandable: Energy (E) the ability to do work or produce heat ; the sum of all potential and kinetic energy in a system

### Chemistry Guide

551534 - Chemistry Guide 1- Contents Question Item Objective Type Skill 1 0102 M03.02.04 Multiple-choice answer Mastery of Problem Solving 2 0099 M03.03.02 Multiple-choice answer Mastery of Concepts 3

### HEAT OF FUSION MECHANICAL EQUIVALENT OF HEAT AND PART A. HEAT OF FUSION

HEAT OF FUSION AND MECHANICAL EQUIVALENT OF HEAT CAUTION: Please handle thermometers gently. Broken mercury-filled thermometers should be taken to Rm. B-31 for disposal as mercury is very toxic. If a red-liquid

### Chapter 5 Thermo. Energy & Chemistry. Energy & Chemistry. Units of Energy. Energy & Chemistry. Potential & Kinetic Energy. Some Basic Principles

1 Energy & Chemistry effrey Mack California State University, Sacramento Chapter 5 Principles of Chemical Reactivity: Energy and Chemical Reactions Questions that need to be addressed: How do we measure

### Calorimeter: A device in which the heat associated with a specific process is measured.

1 CALORIMETRY p. 661-667 (simple), 673-675 (bomb) Calorimeter: A device in which the heat associated with a specific process is measured. There are two basic types of calorimeters: 1. Constant-pressure

### Chemistry Thermochemistry Lesson 10 Lesson Plan David V. Fansler

Chemistry Thermochemistry Lesson 10 Lesson Plan David V. Fansler The Flow of Energy-Heat Objectives: Explain the relationship between energy and heat; Distinguish between heat capacity and specific heat.

### Calorimetry and Thermochemistry

CHEM 121L General Chemistry Laboratory Revision 1.3 Calorimetry and Thermochemistry Learn how to measure Heat flow. Learn about the Specific Heat of substances. Learn about Exothermic and Endothermic chemical

### Chapter 6 Quantities in Chemical Reactions

Chapter 6 Quantities in Chemical Reactions The Meaning of a Balanced Chemical Equation Mole-Mole Conversions Mass-Mass Conversions Limiting Reactants Percent Yield Energy Changes Copyright The McGraw-Hill

### EXPERIMENT 15 FREEZING POINT: A COLLIGATIVE PROPERTY OF SOLUTIONS

EXPERIMENT 15 FREEZING POINT: A COLLIGATIVE PROPERTY OF SOLUTIONS INTRODUCTION Scientists seldom work alone today. Instead they work in teams on projects, sharing the labor of carrying out the experiments

### CHEM 1411, chapter 6. Thermochemistry Exercises

CHEM 1411, chapter 6. Thermochemistry Exercises 1. The heat capacity of 20.0 g of water is 83.7 J/ C. A) True B) False 2. Find the heat absorbed from the surroundings when 15 g of O 2 reacts according

### Chapter 6: Thermochemistry (Chemical Energy) (Ch6 in Chang, Ch6 in Jespersen)

Chapter 6: Thermochemistry (Chemical Energy) (Ch6 in Chang, Ch6 in Jespersen) Energy is defined as the capacity to do work, or transfer heat. Work (w) - force (F) applied through a distance. Force - any

### 3A Energy. What is chemical energy?

3A Energy What is chemical energy? Chemical energy is a form of potential energy which is stored in chemical bonds. Chemical bonds are the attractive forces that bind atoms together. As a reaction takes

### Water Lab. Objective: To distill samples of water that contains volatile and nonvolatile components.

Water Lab I. Distillation Hypothesis: Water can be purified by distillation. Objective: To distill samples of water that contains volatile and nonvolatile components. Materials and Equipment: Sodium chloride,

### Example. c. Calculate the amount of heat (in kj) required to heat 1.00 kg (~1 L) of water at 25 C to its boiling point.

Example When consuming an ice-cold drink, one must raise the temperature of the beverage to 37.0 C (normal body temperature). Can one lose weight by drinking ice-cold beverages if the body uses up about

### H 2 (g) + ½ O 2 (g) H 2 O(l) H o f [NO(g)] = 90.2 kj/mol; H o f [H 2 O(g)] = kj/mol H o f [NH 3 (g)] = kj/mol; H o f [O 2 (g)] =?

Chapter 16 Thermodynamics GCC CHM152 Thermodynamics You are responsible for Thermo concepts from CHM 151. You may want to review Chapter 8, specifically sections 2, 5, 6, 7, 9, and 10 (except work ). Thermodynamics:

### Practice Test Questions:

Practice Test Questions: There are a lot of questions. Please feel free to do a problem, skip around and make sure you are doing all types of problems heat exchange, Hess Law problems, specific heat problems,

### Energy and Chemical Reactions. Characterizing Energy:

Energy and Chemical Reactions Energy: Critical for virtually all aspects of chemistry Defined as: We focus on energy transfer. We observe energy changes in: Heat Transfer: How much energy can a material

### Experiment 4-Heat of Fusion and Melting Ice Experiment

Experiment 4-Heat of Fusion and Melting Ice Experiment In this lab, the heat of fusion for water will be determined by monitoring the temperature changes while a known mass of ice melts in a cup of water.

### UNIT 1 THERMOCHEMISTRY

UNIT 1 THERMOCHEMISTRY THERMOCHEMISTRY LEARNING OUTCOMES Students will be expected to: THERMOCHEMISTRY STSE analyse why scientific and technological activities take place in a variety individual and group

### Thermodynamics- Chapter 19 Schedule and Notes

Thermodynamics- Chapter 19 Schedule and Notes Date Topics Video cast DUE Assignment during class time One Review of thermodynamics 1_thermo_review AND Review of thermo Wksheet 2.1ch19_intro Optional: 1sc_thermo

### PREPARATION FOR CHEMISTRY LAB: COMBUSTION

1 Name: Lab Instructor: PREPARATION FOR CHEMISTRY LAB: COMBUSTION 1. What is a hydrocarbon? 2. What products form in the complete combustion of a hydrocarbon? 3. Combustion is an exothermic reaction. What

### Unit 27 Heat of Neutralization Calorimetry

Unit 27 Heat of Neutralization Calorimetry When reactions occur, energy is always involved. Reactions that absorb energy are called "endothermic" reactions. Reactions that give off energy are called "exothermic"

### Determination of Molecular Mass by Freezing Point Depression

Determination of Molecular Mass by Freezing Point Depression Objectives: To determine the molecular mass of an unknown solid using the colligative property of freezing point depression. Background: When

### CHAPTER 17: THERMOCHEMISTRY. Heat vs. Temperature. Heat vs. Temperature. q = mc T. Heat Capacity vs. Specific Heat

CHAPTER 17: THERMOCHEMISTRY Page 504 539 Heat vs. Temperature ATOM Heat energy= Kinetic energy SUBSTANCE Heat energy = TOTAL Kinetic energy of all atoms in a substance Temperature = AVERAGE Kinetic energy

### Use tongs and wear goggles when removing the samples from the pot of boiling water. Protect your eyes against accidental splashes!

Calorimetry Lab Purpose: Students will measure latent heat and specific heat. PLEASE READ the entire handout before starting. You won t know what to do unless you understand how it works! Introduction:

### Chapter 5 Energy Relationships in Chemistry: Thermochemistry

Chapter 5 Energy Relationships in Chemistry: Thermochemistry In order to study thermochemical changes, we first have to define (a) system that specify part of the universe of interest to us. (b) surrounding

### Bomb Calorimetry Determination of the Energy in a Biodiesel

Bomb Calorimetry Determination of the Energy in a Biodiesel So now we ve got our sample of biodiesel from the previous week, what do we do with it. Well, a fuel is something that ideally is able to be

### I. CALORIMETRY CALORIMETRY

CALORIMETRY I. CALORIMETRY If the process (e.g. chemical reaction, phase conversion) requires heat to proceed, it is said to be endothermic. For endothermic process, q > 0. If the process (e.g. chemical

### System. System, Boundary and surroundings: Nature of heat and work: Sign convention of heat: Unit-7 Thermodynamics

Unit-7 Thermodynamics Introduction: The term Thermo means heat and dynamics means flow or movement.. So thermodynamics is concerned with the flow of heat. The different forms of the energy are interconvertible

### Chapter 5: thermochemstry. Internal Energy: E

Chapter 5: thermochemstry tonight s goals Energy and Enthalpy Review Enthalpies of Reaction Calorimetry Hess Law Enthalpies of Formation Internal Energy: E E = The sum of all kinetic and potential energies

### HEAT OF FORMATION OF AMMONIUM NITRATE

303 HEAT OF FORMATION OF AMMONIUM NITRATE OBJECTIVES FOR THE EXPERIMENT The student will be able to do the following: 1. Calculate the change in enthalpy (heat of reaction) using the Law of Hess. 2. Find

### PREPARATION FOR CHEMISTRY LAB: COMBUSTION

1 1. What is a hydrocarbon? PREPARATION FOR CHEMISTRY LAB: COMBUSTION 2. Give an example of a combustion reaction? 3. What products form in the complete combustion of a hydrocarbon? Are these products

### Molecular Weight of a Volatile Liquid

Molecular Weight of a Volatile Liquid One of the important applications of the Ideal Gas Law is found in the experimental determination of the molecular weight of gases and vapors. In order to measure

### Determination of the enthalpy of combustion using a bomb calorimeter TEC

Determination of the enthalpy of TEC Related concepts First law of thermodynamics, Hess s law of constant heat summation, enthalpy of combustion, enthalpy of formation, heat capacity. Principle The bomb

### ( )( L L)

Chemistry 360 Dr. Jean M. Standard Problem Set 5 Solutions 1. Determine the amount of pressure-volume work performed by 1 mole of water freezing to ice at 0 C and 1 atm pressure. The density of liquid

### Food Calorimeter Experiment Guide

Food Calorimeter Experiment Guide Food Calorimeter INTRODUCTION: The food calorimeter allows students to determine the amount of energy released through the burning of food. This easy to use method involves

### Going back to the original form of the internal energy equation, du = dq + dw expansion + dw other

CALORIMETRY Internal energy is measured in terms of work and heat, du = dq + dw exp + dw other This equation is often applied to the first law of thermodynamics. This law states that the energy of the

### Additivity of Heats of Reaction: Hess s Law

Additivity of Heats of Reaction: Hess s Law Computer 18 In this experiment, you will use a Styrofoam-cup calorimeter to measure the heat released by three reactions. One of the reactions is the same as

### CHEMISTRY 110 Assignment #3 - answers 2011.

1. Titanium metal is used as a structural material in many high tech applications such as in jet engines. What is the specific heat of titanium in J/() if it takes 89.7 J to raise the temperature of a

### 5.2. Determining Enthalpy of Reaction by Experiment. Specific Heat Capacity. 234 MHR Unit 3 Energy Changes and Rates of Reaction

In this section, you will 5.2 Section Preview/ Specific Expectations determine the heat that is produced by a reaction using a calorimeter, and use the data obtained to calculate the enthalpy change for

### PHYSICS 220 LAB #9: CALORIMETRY

Name: Partners: PHYSICS 220 LAB #9: CALORIMETRY If you pour cold cream into a hot cup of coffee, the mixture comes to an intermediate equilibrium temperature. If you put a piece of ice in a glass of water,

### CSUS Department of Chemistry Experiment 4 Chem.1A

Name: Section: Experiment 4: Synthesis of Alum Pre-laboratory Assignment (Read through the experiment before starting!) 1. a) What are the strong acid and strong base used in this synthesis? b) What should

### Specific Heat. Goals and Introduction

Specific Heat Goals and Introduction One process by which the temperature of an object can change is when an exchange of thermal energy, or heat flow, Q, occurs between an object and its surroundings.