8. Thermochemistry

Constant-Pressure Calorimetry

Calorimetry Concept, Examples and Thermochemistry | How to Pass Chemistry

When an 18.6-g sample of solid potassium hydroxide dissolves
in 200.0 g of water in a coffee-cup calorimeter (Figure
5.18), the temperature rises from 23.7 to 44.5 °C. (b) Using
your result from part (a), calculate H (in kJ>mol KOH)
for the solution process. Assume that the specific heat of the
solution is the same as that of pure water.

An empty 4.00-L steel vessel is filled with 1.00 atm of CH41g2 
and 4.00 atm of O21g2 at 300 °C. A spark causes the 
CH4 to burn completely, according to the equation 
CH41g2 + 2 O21g2¡CO21g2 + 2 H2O1g2 
ΔH° = -802 kJ 
(b) What is the final temperature inside the vessel after 
combustion, assuming that the steel vessel has a mass 
of 14.500 kg, the mixture of gases has an average molar 
heat capacity of 21 J>1mol # °C2, and the heat capacity 
of steel is 0.449 J>1g # °C2?

A 115.6 g piece of copper metal at 182.5 ºC is placed into 120.0 mL of methylene chloride at 31.0 ºC within a coffee-cup calorimeter. If the final temperature of the solution is 50.3 ºC, what is the specific heat of methylene chloride? Assume the calorimeter absorbs a negligible amount of heat. The specific heat of copper is&nbsp;4.184 J/g&nbsp;∙&nbsp;ºC and the density of methylene chloride is&nbsp;1.33 g/cm3.

Chemistry - Thermochemistry (26 of 37) Constant Pressure Calorimeter

Constant-Pressure Calorimetry Example 1

Constant-Pressure Calorimetry Example 2

CHEMISTRY 101 - Constant Pressure Calorimetry

Coffee Cup Calorimetry Examples (Constant Pressure)

Instant hot packs contain a solid and a pouch of water. When the pack is squeezed, the pouch breaks and the solid dis- solves, increasing the temperature because of the exothermic reaciton. The following reaction is used to make a hot pack: H2O
LiCl1s2 ¡ Li 1aq2 + Cl 1aq2 ∆H = -36.9 kJ. What is the final temperature in a squeezed hot pack that contains 25.0 g of LiCl dissolved# in 125 mL of water? Assume a specific heat of 4.18 J>1g °C2 for the solution, an initial temperature of 25.0 °C, and no heat transfer between the hot pack and the environment.

You place 75.0 mL of 0.100 M NaOH&nbsp;in a calorimeter at 25.00&nbsp;ºC and carefully add 55.0 mL of 0.200 M HNO3, also at 25.00&nbsp;ºC. After stirring, the final temperature is 53.35&nbsp;ºC. Calculate the enthalpy&nbsp;∆Hrxn (in J/mol) for the formation of water. (Specific heat capacity, Cs, and density of the solution:4.184 J/g∙K and 1.00 g/mL).

A coffee-cup calorimeter of the type shown in Figure 5.18 
contains 150.0 g of water at 25.2 °C. A 200-g block of silver 
metal is heated to 100.5 °C by putting it in a beaker of boiling 
water. The specific heat of Ag(s) is 0.233J>1g # K2. The Ag is 
added to the calorimeter, and after some time the contents 
of the cup reach a constant temperature of 30.2 °C. 
(b) Determine the amount of heat gained by the water. The 
specific heat of water is 4.184 J>1g # K2.

Chemistry - Thermochemistry (31 of 37) Constant Pressure Calorimeter: Ex. 2

 The enthalpy and the internal energy of the system are the same. 

 Internal energy considers both heat and work, while enthalpy is a measure of the heat flow at constant pressure. 

 The magnitude of the enthalpy is less than the magnitude of the internal energy. 

 Correct, enthalpy is equivalent to the heat flow at constant pressure. 

 The magnitude of the enthalpy is greater than the magnitude of the internal energy. 

 The process is exothermic from the surroundings point of view. 

 The process is exothermic from the system's point of view. 

 One statement is true when the definition of internal energy and enthalpy are compared. 

&Delta;E is a measure of the total energy change (both heat and work) in a reaction.

 When gasoline is burned at constant pressure, a certain amount of heat is emitted and work is done.  Which of the following must be true? 

(c) Assume that a chunk of potassium weighing 7.55 g is dropped into 400.0 g of water at 25.0 °C. What is the final temperature of the water if all the heat released is used to warm the water?

When 1.50 g of magnesium metal is allowed to react with 200 mL of 6.00 M aqueous HCl, the temperature rises from 25.0 °C to 42.9 °C. Calculate ΔH in kilojoules for the reaction, assumign that the heat capacity of the calorimeter is 776 J/°C, that the specific heat of the final soltuion is the same as that of water [4.18 J(g·°C)] and that the density of the solution is 1.00 g/mL

When an 18.6-g sample of solid potassium hydroxide dissolves
in 200.0 g of water in a coffee-cup calorimeter (Figure
5.18), the temperature rises from 23.7 to 44.5 °C. (a) Calculate
the quantity of heat (in kJ) released in the reaction.

Calorimetry (Constant-Pressure Calorimeter)

A sample of a hydrocarbon is combusted completely in
O21g2 to produce 21.83 g CO21g2, 4.47 g H2O1g2, and 311 kJ of
heat. (a) What is the mass of the hydrocarbon sample that
was combusted?

A 110.0 g piece of molybdenum metal is heated to 100.0 °C and placed in a calorimeter that contains 150.0 g of water at 24.6 °C. The system reaches equilibirum at a final temeprature of 28.0 °C. Calcualte the specific heat of molybdenum metal in J/g·°C. The specific heat of water is 4.18 J/g·°C

A coffee-cup calorimeter of the type shown in Figure 5.18 
contains 150.0 g of water at 25.2 °C. A 200-g block of silver 
metal is heated to 100.5 °C by putting it in a beaker of boiling 
water. The specific heat of Ag(s) is 0.233J>1g # K2. The Ag is 
added to the calorimeter, and after some time the contents 
of the cup reach a constant temperature of 30.2 °C. 
(d) What would be the final temperature of the system if all 
the heat lost by the silver block were absorbed by the water in 
the calorimeter?

Chapter 09 - 16 - Constant Pressure Calorimetry (coffee cup)

A coffee-cup calorimeter of the type shown in Figure 5.18
contains 150.0 g of water at 25.2 °C. A 200-g block of silver
metal is heated to 100.5 °C by putting it in a beaker of boiling
water. The specific heat of Ag(s) is 0.233J>1g # K2. The Ag is
added to the calorimeter, and after some time the contents
of the cup reach a constant temperature of 30.2 °C. (a) Determine
the amount of heat, in J, lost by the silver block.

Citric acid has three dissociable hydrogens. When 5.00 mL of 0.64 M citric acid and 45.00 mL of 0.77 M NaOH are mixed at an initial temperature of 26.0 °C, the temperature rises to 27.9 °C as the citric acid is neutralized. The combined mixture ahs a mass of 51.6 g and a specific heat of 4.0 J/(g·°C). Assuming that no heat is transferred to the surroundings, cal- culate the enthalpy change for the reaction of 1.00 mol of cit-
ric acid in kJ. Is the reaction exothermic or endothermic?

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2. Atoms & Elements

3. Chemical Reactions

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5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

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24. Transition Metals and Coordination Compounds

[BOOK CHEM] Clutch Version

Hess's Law

Hess's Law involves the use of partial reactions in the determination of the overall enthalpy of reaction.

Nature of Energy

Thermochemistry is the study of matter and energy associated with chemical reactions or physical changes.&nbsp;

Endothermic & Exothermic Reactions

Endothermic and Exothermic Reactions involve the absorbing and releasing of thermal energy respectively.&nbsp;&nbsp;

Heat Capacity

Heat Capacity is the amount of heat required to change the temperature of a substance.&nbsp;

Thermochemical Equations

Thermochemical Equations&nbsp;involve a balanced chemical equation with a given enthalpy value.

Internal Energy

The Internal Energy of a system is the total energy from all forms of kinetic and potential energy.&nbsp;

Kinetic & Potential Energy

Mechanical Energy is the energy associated with an object's velocity (Kinetic Energy) and its position (Potential Energy).&nbsp;

Formation Equations

Formation Equations involve the standard states of elements combining to form 1 mole of product.

Enthalpy of Formation

The Enthalpy of Formation for an element is a key component in determining the enthalpy of reaction.&nbsp;

Thermal Equilibrium

Thermal Equilibrium involves two substances that are in physical contact reaching the same final temperature over time.&nbsp;

Constant-Pressure Calorimetry uses a coffee cup calorimeter to determine the heat transfers occurring in a liquid solution.

Constant-Volume Calorimetry

Constant-Volume Calorimetry uses a bomb calorimeter and a combustion reaction to determine its enthalpy of reaction.&nbsp;

First Law of Thermodynamics

The First Law of Thermodynamics states that energy cannot be created nor destroyed, but instead is transferred.&nbsp;

First Law of Thermodynamics -

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