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

Save this PDF as:

Size: px
Start display at page:

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

## Transcription

1 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- ml graduated cylinders, 150 ml beaker, aluminum slug, magnesium ribbon, magnesium oxide, 1.00 M HCl, 1.00 M NaOH, copper wire. PURPOSE: The purpose of this experiment is to determine the H o for the combustion of magnesium by determining the H o s for reactions which can be combined together according to Hess Law, yielding the H o for the desired reaction. LEARNING OBJECTIVES: By the end of this experiment, the student should be able to demonstrate the following proficiencies: 1. Construct and use a calorimeter. 2. Use a calorimeter to examine heat transfer and determine the specific heat of a metal. 3. Determine the heat capacity of a calorimeter using a reaction with known H o. 4. Determine a set of reactions which, after applying Hess Law, yield the H o for the desired reaction. 5. Devise procedures to address experimental challenges associated with the reactions. 6. Use a spreadsheet program for data manipulation, graphing, and regression analysis. PRE-LAB: Complete the pre-lab questions on page E12J-11 before lab. DISCUSSION: The First Law of Thermodynamics is the Law of Conservation of Energy, which states that energy can neither be created nor destroyed the total energy of the universe is a constant. A fire or a chemical explosion is just the result of converting the chemical energy of the fuel or explosive into thermal and mechanical energy of the products and the surrounding air. Objects near a fire increase in temperature because energy is transferred in a process called heating; the energy exchanged is the amount of heat (q). Objects near an explosion are moved because energy is transferred in a process called doing work; the energy exchanged is the amount of work done (w). Our primary interest here is with heat transfers (the thermo in thermodynamics). These heat transfers can take place between two objects at different temperatures, and they also can accompany physical or chemical changes (i.e., reactions). Calorimetry is a technique for measuring heat transfers; it makes use of an insulated container called a calorimeter. Qualitatively, the process of heat transfer that occurs in a calorimeter is very familiar to us. We all recognize that a cup of hot coffee left in a cool room will get colder, and eventually will become the same temperature as the room. Of course, the thermal energy of the coffee cannot be lost; it is simply moved into the rest of the room. The coffee gets measurably colder, while the room gets warmer, albeit imperceptibly. The air (and the walls, furniture, etc.) of the room serves as a thermal bath to absorb the heat released by the coffee. The same thing happens in a calorimeter. If a hot object, like an aluminum slug, is dropped into a cold sample of water, the water acts the thermal bath and absorbs the heat; the process stops when both water and slug are at the same temperature, a situation called thermal equilibrium. If the whole process is conducted in an insulated container, like a Styrofoam cup, then no heat is lost to the room. In a thermodynamic sense, the hot Al slug is the system, and the water the surroundings. Energy lost by the system is gained by the surroundings. The insulated cup acts as the whole experimental universe, and the total energy within the cup must remain constant, as dictated by the First Law. As long as there is no phase change, a transfer of energy into or out of a sample of matter will result in a temperature change. The magnitude of the temperature change will depend on the kind of material, its amount (i.e., the mass m or number of moles n), and how much energy is transferred. The relation between the amount of energy transferred in the form of heat, q, and the temperature change of the object, D T, can be written as: q = c m D T or q = c m n D T (1) E12J-1

2 (As is always true in thermodynamic calculations, D represents a difference between the final and initial values: DT = T final - T initial. ) The proportionality constants in the equation above are different versions of the heat capacity of the object. In the first equation, the constant c is the specific heat capacity (commonly called just specific heat ). Typical units for the specific heat are Joules per gram per o Celsius, or J g -1 o C -1. Basically, it tells you how many Joules of heat you have to add or remove to change the temperature of one gram of the material by one degree Celsius. The constant c m in the second equation is the molar heat capacity; it relates similar information, except it pertains to warming or cooling one mole of material, rather than one gram. Which equation (and constant) you use depends only on your choice of using mass or moles to describe the quantity, but you must be consistent. Again, either one is specific to the substance. If a number of different substances are all being subjected to the same heat input (as with the walls, air and furniture in the room absorbing heat from the coffee), it is usually necessary to use a generic total heat capacity, c tot. There, it represents the amount of heat transfer required to change the temperature of the whole assembly by one o C q = c tot D T (2) Use of this form will be required in our measurements of the heat of reaction, since the whole calorimeter assembly will involve a Styrofoam cup and its lid, and the dilute acid solution, magnetic stir bar and the end of a thermometer within it. No matter which form of the D T expression is used, the general equation for calorimetry works the same way, since the calorimeter again represents the experimental universe, and we are simply watching heat move from one part of that universe to another. To use the example above, the energy lost by the aluminum slug (q Al ) must be gained by the water (q water ). The total energy of the universe is constant, so q Al + q water = 0 (3) Or, this could be rearranged as q Al = q water (4) The negative sign simply results because one object gains heat energy (the water) while the other (Al) loses it. Although the magnitudes of the energy change are the same, the directions are opposite. Both substances have their own unique values of specific heat, and each has a different mass, so each must be represented separately: q Al = c Al m Al D T Al (5) q water = c water m water D T water (6) When resubstituted into the overall calorimetry expression (Eq. 4), the final result is: q Al = q water or c Al m Al D T Al = c water m water D T water (7) Note that the values of T will be different for each substance, even though their final temperatures, T f, are the same, once thermal equilibrium is reached. When measuring energy changes associated with a chemical reaction, the principle is the same. For example, in an exothermic reaction, the reaction will release heat to the surroundings. An exothermic reaction run in a calorimeter acts just like the aluminum slug and water in the simple heat transfer experiment above. The heat transfer associated with the reaction is q rxn ; that associated with the calorimeter is q cal. The law of conservation of energy must hold, so q rxn + q cal = 0 or q rxn = q cal (8) As described above, the calorimeter is an assembly of several different materials, and so its heat equation q cal is best described using the total heat capacity (Eq. 2). Then q rxn = q cal becomes q rxn = c tot cal D T cal (9) E12J-2

3 Again, the negative sign is required because of the direction of the heat change, and reflects the fact that an exothermic reaction (negative q) results in a positive T (temperature increase). In a calorimetry experiment, a reaction is performed inside a calorimeter and the resulting temperature change of the calorimeter is measured. If we know the total heat capacity of the calorimeter and its contents, and can measure the temperature change when the reaction occurs, then we can determine the amount of heat liberated by the reaction. Alternately, if we know the amount of heat transferred, we can determine the heat capacity of the calorimeter by simply using the equation in reverse. As a final theoretical detail, if the heat of reaction is measured in a constant-pressure calorimeter (e.g., a coffee-cup calorimeter), then q rxn = q p = D H (The subscript p emphasizes that the heat of reaction was measured at constant pressure.) (10) Thus we are able to measure D H, which is a goal of the experiment. The correct determination of T for a reaction requires careful consideration of two key issues: (1) reactions do not occur instantaneously, and (2) calorimeters are not perfectly insulated from their surroundings, thus allowing heat energy to slowly enter or escape from the calorimeter over time. Consider an exothermic reaction which occurs in a hypothetical calorimeter which is perfectly insulated. In this case, whether the reaction occurs instantaneously or not, all of the heat produced by the reaction will remain in the calorimeter, resulting in the same final temperature, and hence the same T. Now consider a hypothetical exothermic reaction which occurs instantaneously, but in a realistic calorimeter which is not perfectly insulated. In this case, the temperature of the calorimeter would diminish over time due to the gradual escape of heat energy to the surroundings. The final temperature Instantaneous reaction, perfectly insulated calorimeter to be used in determining T in this case is 30 actually the maximum temperature reached Tf immediately after reaction occurs, since this 28 temperature change is due exclusively to the 26 heat produced in the reaction, and no Instantaneous reaction, partially insulated calorimeter escaping of heat to the surroundings has 24 occurred yet. These three hypothetical cases T i Non-instantaneous reaction, perfectly insulated calorimeter are all depicted on the following temperature 22 vs. time graph: Temp ( o C) Time (min) For real calorimeter experiments, reactions neither occur instantaneously nor are calorimeters perfectly insulated. Thus, during an exothermic reaction the temperature of the calorimeter increases initially, but never has a chance to reach the correct maximum final temperature since heat is escaping to the surroundings even while the reaction is proceeding toward completion. The best way to account for these experimental difficulties, thereby obtaining a very good estimate of the correct final temperature, is to linearly extrapolate the gradual cooling portion of the temperature vs. time graph back to the initial time of mixing. This is the temperature that the calorimeter would have reached if all the heat energy from the reaction had remained absorbed by the calorimeter. This approach to obtaining the correct final temperature is depicted on the following temperature vs. time graph, and can easily be accomplished using a spreadsheet (see Appendix O of the Plebe Chemistry Lab Manual): 30 T f 28 Non-instantaneous reaction, partially insulated calorimeter (extrapolate cooling portion of curve back to time of mixing) Temp ( o C) T i Time (min) E12J-3

5 time values every 5-10 seconds for about one minute, and every seconds for about 2 minutes after that. Be sure to swirl the cup frequently. 5. Remove the slug from the water, empty the water into a sink, and dry off the slug and the inside of the cup and lid. Answer in-lab questions #6 and #7 on pages E12J-10. Part C: Measuring the total heat capacity of the calorimeter and its contents 1. Calorimetry requires that the heat capacity of the calorimeter and its contents be known. In this experiment, the calorimeter will consist of a Styrofoam cup and lid. It will contain a stir bar, thermometer, and a dilute solution. You will need to measure how much the temperature of the calorimeter and its contents changes when they absorb a known amount of heat. To produce a known amount of heat, you will perform the following acid-base neutralization reaction, for which H o is well known: H + (aq) + OH - (aq) H 2 O(l) D H o = kj 2. Place the magnetic stir bar into a clean, dry Styrofoam cup. 3. Rinse a clean graduated cylinder with a few milliliters of 1.00 M HCl and transfer 50.0 ml of 1.00 M HCl into the cup. 4. Place the cup on the magnetic stirrer and begin stirring gently. (Why gently?) 5. After rinsing the graduated cylinder with distilled water and with a few milliliters of 1.00 M NaOH, obtain a 50.0 ml sample of 1.00 M NaOH. 6. Record the molarity and volume of each solution used. 7. Before mixing, measure the temperature of the two solutions. (Rinse and dry the thermometer between readings). Record the average of the two temperatures. This is the initial temperature (T i ). 8. Working quickly, note the time (time = 0 s) when the NaOH solution is added to the Styrofoam cup, then put on the lid, and place the thermometer into the solution. (The thermometer must be supported in some way to prevent the cup from tipping over.) 9. Record the time and temperature every seconds for a total of 8 minutes. The time intervals can be increased as the rate of temperature change decreases. 10. When data collection is completed, rinse the calorimeter with distilled water and dry as completely as possible. Important: For this and all subsequent experiments, use a total solution volume of ml. Part D: Measuring D H o for the reaction of Mg or MgO with HCl Your instructor will assign you a specific reaction to study, and give you either a target mass of reagent or target T to work for. See your instructor to obtain these assignments. For students assigned to study the Mg/acid reaction: 1. In part A, you probably observed that the magnesium metal floated on top of the acid solution as it reacted with it. (Think about why this is a problem.) E12J-5

7 DATA ANALYSIS: Part C: Measuring the total heat capacity of the calorimeter and its contents 1. Construct a plot of temperature versus time with Excel and determine the highest temperature (T f ) that would have been achieved if the calorimeter was perfectly insulated (see DISCUSSION section). Use this final temperature to calculate the temperature change ( T = T f - T i ) of the calorimeter. (Refer to Appendix O in the lab manual for help in determining T f using Excel.) 2. Using the following information and the amounts of reactants used in the experiment, calculate the heat (in Joules) produced by the reaction. H + (aq) + OH - (aq) H 2 O(l) H o = kj 3. Calculate the total heat capacity of the calorimeter (c tot cal ) in J/ o C. Part D: Measuring D H o for the reaction of Mg or MgO with HCl 1. Calculate the number of moles of Mg or MgO that were consumed in the reaction that you studied. 2. Determine the temperature change ( T = T f - T i ) for the reaction you studied by constructing a temperature versus time plot on the graph paper provided. (Your instructor will tell you whether you must reproduce this graph in Excel.) 3. Using the total heat capacity of your calorimeter (c tot cal ) and the temperature change, calculate the heat produced by the reaction that you studied (q rxn = H o ). 4. Report the number of moles of Mg or MgO and your calculated H o (q rxn ) to the class. 5. Create an Excel spreadsheet that lists the results from the entire class (moles of reactant and H o for each of the two reactions studied.) 6. Use Excel to graph the class data for both reactions (two graphs) and use the graphs to determine the average value for H o per mole of magnesium, and the average value for H o per mole of magnesium oxide. (Think about which data you should plot on the y-axis.) 7. Combine these results and the H o for the reaction below to obtain H o for the combustion of magnesium. H 2 (g) + ½ O 2 (g) H 2 O(l) H o = kj E12J-7

8 QUESTIONS FOR CONSIDERATION: 1. Using available thermodynamic tables of H o f (standard enthalpy of formation), determine the H o values for the magnesium/acid and magnesium oxide/acid reactions and compare with your experimentally determined values. Explain any differences. H f (Mg 2+ ) = kj/mol 2. Is the combustion reaction for magnesium the same as the formation reaction for magnesium oxide? Does this mean that the H o obtained is the same as the H o f for magnesium oxide? Compare your experimental value with that found in the table of thermodynamic properties in your textbook. Determine the percent error. 3. Sketch the temperature vs. time graph that you would expect for an endothermic reaction carried out in a calorimeter similar to the one used in the experiment (assume the reaction is not instantaneous and that the calorimeter is not perfectly insulated). 4. Could the same procedures be applied for determining the H o for the combustion of aluminum metal as were used in this experiment? Show how the analogous reactions would combine together, applying Hess Law, to yield the H o for the combustion reaction. 5. Using thermodynamic tables and your calorimeter heat capacity, predict the T if 1.00 g of aluminum oxide completely reacted with hydrochloric acid. H f (Al 3+ ) = kj/mol 6. If the material absorbing the heat produced by reaction were limited to just the water, what would be the expected heat capacity of your calorimeter? How does the experimentally determined heat capacity compare? 7. In Parts C and D, we assumed that the heat of reaction was equal to the standard enthalpy change. For both Part C and Part D, discuss whether or not this was a good assumption. E12J-8

9 Name Section IN-LAB QUESTIONS Experiment 12J Complete these questions during lab. 1. Write the balanced chemical equation for combustion of one mole of magnesium metal. (The coefficient in front of Mg should be 1, but other coefficients may be fractional coefficients. We are doing this because we want to determine H o per mole of magnesium.) 2. Why would it be difficult to study the combustion of magnesium directly using a simple water-filled calorimeter? 3. Write the balanced molecular, complete ionic, and net ionic equations for the reaction of magnesium metal with hydrochloric acid. (Hint: the Activity Series table may help you determine what the products are in this reaction.) Molecular: Complete ionic: Net ionic: 4. Write the balanced molecular, complete ionic, and net ionic equations for the reaction of solid magnesium oxide with hydrochloric acid. (Hint: Magnesium oxide is a base!) Molecular: Complete ionic: Net ionic: E12J-9

10 5. Combine the two deduced reactions (net ionic equations) and the given reaction so that the 3 reactions add to give the desired reaction (combustion of one mole of magnesium). The given reaction is: H 2 (g) + ½ O 2 (g) H 2 O (l) 6. Fill in the following values from your data of Part B. Aluminum Mass (g) Initial Temp. ( o C) Final Temp. ( o C)* D T ( o C) Water *Use the maximum temperature as the final temperature of the Al and water, unless directed by your instructor to perform the temperature-time extrapolation described in the Discussion section. Use of the maximum temperature is an approximation that works reasonably well in Part B because you do not have to wait for an entire samp le to react. 7. Use the data above and Eq. 7 to calculate the specific heat of aluminum. The specific heat of water is J g -1 o C -1. Have your instructor check your result. 8. Based on the Activity Series, identify two different metals that could be used as weights to keep the magnesium metal submerged in the hydrochloric acid solution which would not react with the acid. Explain your answer. E12J-10

11 Name Section Date PRE-LAB QUESTIONS Experiment 12J 1. Plot the following set of temperature vs. time data using a spreadsheet program, with time on the x-axis and temperature on the y-axis. Extrapolate the linear portion of the graph and determine T f of the reaction for which the data have been recorded. (Refer to the Excel directions in Appendix O.) Include your properly formatted graph with your Pre-lab. T f = T = Time (minutes) Temperature ( C) o Review the following websites: Services/Fires_and_Explosions/Magnesium_Fire/magnesium_fire.html a. List 2 military applications for the reaction studied in this experiment. Mg (s) + 2 O 2 (g) MgO (s) i. ii. b. True or False: Water should be used to put out a Magnesium fire. (Hint: watch the video on the website.) 3. Use Hess s Law to determine H f for CaO: Ca (s) + ½ O 2 (g) CaO (s) Ca (s) + 2 H + (aq) Ca 2+ (aq) + H 2 (g) H = kj 2 H 2 (g) + O 2 (g) 2 H 2 O (l) H =! kj CaO (s) + 2 H + (aq) Ca 2+ (aq) + H 2 O (l) H = kj H f (CaO) = E12J-11

### 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

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

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

### 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.

### 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

### 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

### 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

### 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

### 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

### 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 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.

### 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

### 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

### 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

### 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

### 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

### 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: 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

### 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

### 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

### 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)

### 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

### 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

### 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

### 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

### 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

### 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

### 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

### LAB FOUR. Name. Lab Partner(s) Section Date. In this experiment you will use calorimetry to determine the specific heat of a metal.

Name Lab Partner(s) Section Date Specific Heat of a Metal Objective In this experiment you will use calorimetry to determine the specific heat of a metal. Introduction When a substance is heated, the motion

### 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

### 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

### 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

### 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,

### Experiment 25: Calorimetry

Aaron Bunch CHEM 111 Morning Lab 27 October 2014 Experiment 25: Calorimetry Conclusion: The unknown metal #14 has a specific heat of 0.36 J/g C; the heat of neutralization of HCl and NaOH is -53.0 kj/mol

### 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

### Calorimetry Lab - Specific Heat Capacity

Introduction Calorimetry Lab - Specific Heat Capacity Experience tells us that if a hot piece of metal is added to water, the temperature of the water will rise. If several different metals having 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

### 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

### 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"

### 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

### 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

### 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

### 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

### Reaction of Magnesium with Hydrochloric Acid (Gas Laws) Chemicals Needed:

Reaction of Magnesium with Hydrochloric Acid (Gas Laws) Your Name: Date: Partner(s) Names: Objectives: React magnesium metal with hydrochloric acid, collecting the hydrogen over water. Calculate the grams

### 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.

### 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

### CALORIMETRY EXPERIMENT A ENTHALPY OF FORMATION OF MAGNESIUM OXIDE

A-1 CALORIMETRY EXPERIMENT A ENTHALPY OF FORMATION OF MAGNESIUM OXIDE INTRODUCTION This experiment has three primary objectives: 1. Find the heat capacity (Cp) of a calorimeter and contents (calibration).

### 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

### 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

### Thermochemistry. Thermochemistry 1/25/2010. Reading: Chapter 5 (omit 5.8) As you read ask yourself

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?

### 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

### SPECIFIC HEAT. Roster Number: Pre-Lab Questions Page Instructor: 2. Define specific heat, water equivalent and heat capacity of a body.

SPECIFIC HEAT Name: Class: Roster Number: Pre-Lab Questions Page Instructor: 1. List the symbol and at least two units for specific heat.,, 2. Define specific heat, water equivalent and heat capacity of

### 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

### thermometer as simple as a styrofoam cup and a thermometer. In a calorimeter the reactants are placed into the

Thermochemistry Readin assinment: Chan, Chemistry 10 th edition, pp. 249-258. Goals We will become familiar with the principles of calorimetry in order to determine the heats of reaction for endothermic

### 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

### 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,

### 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

### 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:

### Thermodynamics Experiment The Enthalpy of H 2 O 2 Decomposition in Aqueous Solution

Thermodynamics Experiment The Enthalpy of H 2 O 2 Decomposition in Aqueous Solution OBJECTIVES 1. To illustrate the use of calorimetry in the experimental measurement of thermodynamic data. 2. To illustrate

### 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

### Name: Introduction to Calorimetry

Name: Introduction to Calorimetry Purpose: The goal of this experiment is to gain experience in the practice of calorimetry; the main method by which chemists measure the energy changes in chemical reactions.

### Determining the Effectiveness of Container Lids on Heat Absorption: Measuring Heat of Reaction for NaOH(aq) and HCl(aq)

SCHOLARS DAY REVIEW 27 SCHOLARS DAY REVIEW VOLUME 2 Determining the Effectiveness of Container Lids on Heat Absorption: Measuring Heat of Reaction for NaOH(aq) and HCl(aq) Christine L. Burton Faculty Sponsor:

### 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

### 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

### Specific Heat (Temperature Sensor)

43 Specific Heat (Temperature Sensor) Thermodynamics: Calorimetry; specific heat Equipment List DataStudio file: 43 Specific Heat.ds Qty Items Part Numbers 1 PASCO Interface (for one sensor) 1 Temperature

### 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

### Recovery of Elemental Copper from Copper (II) Nitrate

Recovery of Elemental Copper from Copper (II) Nitrate Objectives: Challenge: Students should be able to - recognize evidence(s) of a chemical change - convert word equations into formula equations - perform

### Experiment 12E LIQUID-VAPOR EQUILIBRIUM OF WATER 1

Experiment 12E LIQUID-VAPOR EQUILIBRIUM OF WATER 1 FV 6/26/13 MATERIALS: PURPOSE: 1000 ml tall-form beaker, 10 ml graduated cylinder, -10 to 110 o C thermometer, thermometer clamp, plastic pipet, long

### 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

### SOLUTION CALORIMETRY

Experiment 7 SOLUTION CALORIMETRY Prepared by Stephen E. Schullery and Ross S. Nord, Eastern Michigan University PURPOSE Measure the heats of two simple reactions and use Hess's Law to theoretically predict

### 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

### Chemistry 1215 Experiment #10 The Reaction of Zinc and Iodine: The Combination of Two Elements

Chemistry 1215 Experiment #10 The Reaction of Zinc and Iodine: The Combination of Two Elements Objective The objective of this experiment is to perform a combination reaction by reacting elemental zinc

### Carbonate to Halide Conversion

Conversion Objective The theoretical yield of the reaction product and the ratio of products to reactants will be predicted using the Law of Conservation of Matter and the Law of Definite Composition.

### 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

### 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

### 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.

### 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.

### The Enthalpy of Formation of Camphor by Bomb Calorimetry 1

The Enthalpy of Formation of Camphor by Bomb Calorimetry 1 Purpose: The enthalpy of combustion of camphor will be determined in a bomb calorimeter. The enthalpy of formation of camphor will be calculated

### 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

### 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

### Category 5 points 4 points 3 points 2 points 1 point 0 points Participation Participated fully. Mostly on-task. Safety reminders needed.

Lab Report Rubric Category 5 points 4 points 3 points 2 points 1 point 0 points Participation Participated fully Mostly on-task Minimal and Safety participation Prelab /10 Observations Data Units & Significant

### THREE CHEMICAL REACTIONS

THREE CHEMICAL REACTIONS 1 NOTE: You are required to view the podcast entitled Decanting and Suction Filtration before coming to lab this week. Go to http://podcast.montgomerycollege.edu/podcast.php?rcdid=172

### EXPERIMENT 7 Reaction Stoichiometry and Percent Yield

EXPERIMENT 7 Reaction Stoichiometry and Percent Yield INTRODUCTION Stoichiometry calculations are about calculating the amounts of substances that react and form in a chemical reaction. The word stoichiometry

### CHEMICAL REACTIONS OF COPPER AND PERCENT YIELD KEY

CHEMICAL REACTIONS OF COPPER AND PERCENT YIELD Objective To gain familiarity with basic laboratory procedures, some chemistry of a typical transition element, and the concept of percent yield. Apparatus

### Chemistry 212 VAPOR PRESSURE OF WATER LEARNING OBJECTIVES

Chemistry 212 VAPOR PRESSURE OF WATER LEARNING OBJECTIVES The learning objectives of this experiment are to explore the relationship between the temperature and vapor pressure of water. determine the molar

### 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

### LAB SEVEN. Carbonate to Halide Conversion

Name Lab Partner(s) Section Date: Carbonate to Halide Conversion Objective The theoretical yield of the reaction product and the ratio of products to reactants will be predicted using the Law of Conservation

### 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

### Exploring Energy Changes: Endothermic and Exothermic Reactions. Introduction

Exploring Energy Changes: Endothermic and Exothermic Reactions Introduction The story of chemistry is the story of change physical change, chemical change, and energy change. Energy in the form of heat

### 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

### UC Irvine FOCUS! 5 E Lesson Plan

UC Irvine FOCUS! 5 E Lesson Plan Title: Exothermic verses Endothermic Grade Level and Course: 8 th Grade Physical Science & 9-12 High School Chemistry Materials: 100 ml beakers or plastic cups.1 M CH3COOH

### Exp 13 Volumetric Analysis: Acid-Base titration

Exp 13 Volumetric Analysis: Acid-Base titration Exp. 13 video (time: 47:17 minutes) Titration - is the measurement of the volume of a standard solution required to completely react with a measured volume

### Specific Heats of Metals

Johnson 1 Cameron Johnson Jun Li Physics 222 March 6, 2013 Specific Heats of Metals Abstract The purpose of this lab is to determine the specific heat of various types of metals by adding a known amount

### Lab: Specific Heat of Metals PHYSICS: CHAPTER 21: HEAT

Name Date Period Lab: Specific Heat of Metals PHYSICS: CHAPTER 21: HEAT Background: Almost everyone has noticed that some foods remain hot much longer than others. Boiled onions and moist squash on a hot

### What is a Chemical Reaction?

Lab 8 Name What is a Chemical Reaction? Macroscopic Indications and Symbolic Representations Pre-Lab Assignment This written pre-lab is worth 25% (5 POINTS) of your lab report grade and must be turned

### Determination of an Empirical Formula and % Composition

Chem 110 Lab Clark College Determination of an Empirical Formula and % Composition Percent composition will be discussed in your text, lecture and in lab. This concept is often used to determine how many

### Experiment 30 ENERGY CONTENT OF FUELS

Experiment 30 ENERGY CONTENT OF FUELS FV 8/12/2014 MATERIALS: 12-oz. aluminum beverage can with top cut out and holes on side, thermometer, 100 ml graduated cylinder, 800 ml beaker, long-stem lighter,