8. Thermochemistry

Internal Energy

Thermodynamics - Internal Energy

(c) By what means can the internal energy
of a closed system increase?

Calculate the work done in joules by a chemical reaction if the volume increases from 3.2 L to 3.4 L against a constant external pressure of 3.6 atm. What is the sign of the energy change?

During a deep breath, our lungs expand about 2.0 L against
an external pressure of 101.3 kPa. How much work is involved
in this process (in J)?

What is the difference between the internal energy change ∆E and the enthalpy change ∆H? Which of the two is mea- sured at constant pressure and which at constant volume?

The change in internal energy for the combustion of 1.0 mol
of octane at a pressure of 1.0 atm is 5084.3 kJ. If the change in
enthalpy is 5074.1 kJ, how much work is done during the
combustion?

A reaction inside a cylindrical container with a movable
RAN piston causes the volume to change from 12.0 L to 18.0 L while the pressure outside the container remains constant at 0.975 atm. (The volume of a cylinder is V = pr2h, where h is the height; 1 L # atm = 101.325 J.)
(a) What is the value in joules of the work w done during the reaction?

A reaction inside a cylindrical container with a movable
RAN piston causes the volume to change from 12.0 L to 18.0 L while the pressure outside the container remains constant at 0.975 atm. (The volume of a cylinder is V = pr2h, where h is the height; 1 L # atm = 101.325 J.)
(b) The diameter of the piston is 17.0 cm. How far does the piston move?

For which of the following reactions are ΔE and ΔH equal? 
(a) CO2(g) + H2O(l) → H2CO
(b) 2 NaHCO3 (s) → Na2CO3(s) + H2O(g) + CO2(g)
(c) 2 H2(g) + O2(g) → 2 H2O(g)
(d) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)

The enthalpy change for the reaction of 50.0 mL of ethylene with 50.0 mL of H2 at 1.5 atm pressure (Problem 9.51) is
∆H = -0.31 kJ. What is the value of ∆E?

The internal energy of the system:ΔE = q + w

The average human lung expands by about 0.50 L during
each breath. If this expansion occurs against an external pressure
of 1.0 atm, how much work (in J) is done during the expansion?

Redraw the following diagram to represent the situation (b) when work has been lost by the system. <img src="https://lightcat-files.s3.amazonaws.com/problem_images/3cf49e9009c6f2c0-1675352839146.jpg" alt="" />

 A system gains energy as heat and does work on the surroundings. 

 If the work done by the system is greater than the heat gain, the internal energy of the system will decrease. 

 A system loses energy as heat and has work done on it by the surroundings. 

 If the heat loss is greater than the work done, the internal energy of the system will decrease. 

 A system loses energy as heat and does work on the surroundings. 

 This set of conditions results in a net decrease in the internal energy of the system. 

 A system gains energy as heat and has work done on it by the surroundings. 

 Correct, both processes increase the energy of the system. 

Recall: &Delta;E=q+w

 Which of the following processes must always result in a net increase in internal energy of the system? 

A system releases 622 kJ of heat and does 105 kJ of work on the surroundings.
What is the change in internal energy of the system?

The air within a piston equipped with a cylinder absorbs 565 J of
heat and expands from an initial volume of 0.10 L to a final volume
of 0.85 L against an external pressure of 1.0 atm. What is
the change in internal energy of the air within the piston?

What is the enthalpy change (ΔH) for a reaction at a constant pressure of 1.00 atm fi the internal energy chagne (ΔE) is 44.0 kJ and the volume increase is 14.0 L? (1 L-atm = 101.325 J)

Internal Energy Introduction

For the isothermal expansion of a gas into a vacuum, ΔE = 0, q = 0, and w = 0. (b) Explain why no work is done by the system during this process.

Calculate E and determine whether the process is endothermic
or exothermic for the following cases: (a) q = 0.763 kJ
and w = -840 J.

The diagram shows four states of a system, each with different
internal energy, E. (c) Write an expression
for the difference in energy between State C and State D.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/103237bf7f4a96c8-1663016214017.jpg" alt="" />

When 1 mol of a fuel burns at constant pressure, it produces
3452 kJ of heat and does 11 kJ of work. What are ΔE and ΔH for
the combustion of the fuel?

SECOND LAW OF THERMODYNAMICS | Easy & Basic

First law of Thermodynamics | Physics

At a constant pressure of 0.905 atm, a chemical reaction takes place in a cylindrical container with a movable piston having a diameter of 40.0 cm. During the reaction, the height of the piston drops by 65.0 cm. (The volume of a cylinder is
V=pr2h,wherehistheheight;1Latm=101.3J.)
(a) What is the change in volume in liters during the
reaction?

When a sample of a hydrocarbon fuel is ignited and burned in oxygen, the internal energy decreases by 7.20 kJ. If 5670 J of
heat were transferred to the surroundings, what is the sign and magnitude of work? If the reaction took place in an environ- ment with a pressure of 1 atm, what was the volume change?

A gas is confined to a cylinder fitted with a piston and an
electrical heater, as shown here:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6833764776caef6d-1664379484011.jpg" alt="" />
Suppose that current is supplied to the heater so that 100 J of
energy is added. Consider two different situations. In case (1)
the piston is allowed to move as the energy is added. In case
(2) the piston is fixed so that it cannot move. (a) In which
case does the gas have the higher temperature after addition
of the electrical energy?

(d) For a reversible isothermal process, write an expression for ΔE in terms of q and w and an expression for ΔS in terms of q and T.

A reactiont akes place at a constant pressure of 1.10 atm with an internal energy change (ΔE) of 71.5 kJ and a volume decrease of 13.6 L. What is the enthalpy change (ΔH) for the reaction? (1 L-atm = 101.325 J)

Consider the accompanying energy diagram. (a) Does this
diagram represent an increase or decrease in the internal energy
of the system?
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/a6ad504bb5e06881-1664299381059.jpg" alt="" />

Introduction to Internal Energy of Solids, Liquids, and Gases

 There is another state function listed. 

 the distance traveled between two cities 

 The distance traveled can vary depending on the route actually traveled. 

 Correct, neither of these quantities depends on the pathway taken from the initial state to the final state. 

 A state function depends only on the state of the system, not on how the system arrived at that state. 

 Which of the following represents a state function? 

How much work (in J) is involved in a chemical reaction if
the volume decreases from 33.6 L to 11.2 L against a constant
pressure of 90.5 kPa?

A gas reaction is allowed to take place in a canister while submerged in water at a temperature of 25oC. The gas expands and does P-V work on the surroundings equal to 385 J. At the same time, the temperature of the water decreases to 20oC as the energy in the gas reaction reaches 364 J. What is the change in energy of the system?&nbsp;

A gas is compressed from an initial volume of 5.55 L to a final
volume of 1.22 L by an external pressure of 1.00 atm. During the
compression the gas releases 124 J of heat. What is the change
in internal energy of the gas?

At a constant pressure of 0.905 atm, a chemical reaction takes place in a cylindrical container with a movable piston having a diameter of 40.0 cm. During the reaction, the height of the piston drops by 65.0 cm. (The volume of a cylinder is
V=pr2h,wherehistheheight;1Latm=101.3J.)
(b) What is the value in joules of the work w done during
the reaction?

The kinetic energy of a rolling billiard ball is given by
KE = 12 mv2. Suppose a 0.17-kg billiard ball is rolling down a
pool table with an initial speed of 4.5 m/s. As it travels, it loses
some of its energy as heat. The ball slows down to 3.8 m/s and
then collides head-on with a second billiard ball of equal mass.
The first billiard ball completely stops and the second one rolls
away with a velocity of 3.8 m>s. Assume the first billiard ball is
the system. Calculate q.

An unknown gas expands in a container increasing the volume from 4.3 L to 8.2 L at a constant pressure of 931 mmHg. Calculate the internal energy of the system if the system absorbs 2.3 kJ of energy.&nbsp;

Identify each energy exchange as primarily heat or work and
determine whether the sign of ΔE is positive or negative for the
system.
a. Sweat evaporates from skin, cooling the skin. (The evaporating
sweat is the system.)
b. A balloon expands against an external pressure. (The contents
of the balloon is the system.)
c. An aqueous chemical reaction mixture is warmed with an
external flame. (The reaction mixture is the system.)
Identify energy exchanges as primarily heat or work.

Identify each energy exchange as primarily heat or work and
determine whether the sign of ΔE is positive or negative for the
system.
a. Sweat evaporates from skin, cooling the skin. (The evaporating
sweat is the system.)
b. A balloon expands against an external pressure. (The contents
of the balloon is the system.)
c. An aqueous chemical reaction mixture is warmed with an
external flame. (The reaction mixture is the system.)
Identify energy exchanges as primarily heat or work.
Determine whether the sign of E is positive or negative for the system.

Ethyl chloride 1C2H5Cl2, a substance used as a topical anes-thetic, is prepared by reaction of ethylene with hydrogen chloride: 
C2H41g2 + HCl1g2 ¡ C2H5Cl1g2 ΔH° = - 72.3 kJ 
How much PV work is done in kilojoules, and what is the value of ΔE in kilojoules if 89.5 g of ethylene and 125 g of HCl are allowed to react at atmospheric pressure and the volume change is - 71.5 L?

A sample of gas is contained in a cylinder-and-piston arrangement.
There is an external pressure of 100 kPa. The gas
undergoes the change in state shown in the drawing. 
(b) Now assume that the cylinder and piston are
made up of a thermal conductor such as a metal. During the
state change, the cylinder gets colder to the touch. What is
the sign of q for the state change in this case? Describe the
difference in the state of the system at the end of the process
in the two cases. What can you say about the relative values
of E?

The diagram shows four states of a system, each with different
internal energy, E. (a) Which of the states of the system
has the greatest internal energy?
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/cf790f556b198210-1660749817754.jpg" alt="" />

Under what circumstances are ΔE and ΔH essentially equal?

A reaction is carried out in a cylinder fitted with a movable piston. The starting volume is V = 5.00 L, and the appa- ratus is held at constant temperature and pressure. Assum- ing that ∆H = -35.0 kJ and ∆E = -34.8 kJ, redraw the piston to show its position after reaction. Does V increase,
decrease, or remain the same? <img src="https://lightcat-files.s3.amazonaws.com/problem_images/748bb25bcf900e46-1669759641105.jpg" alt="" />

A system absorbs 196 kJ of heat and the surroundings do 117 kJ
of work on the system. What is the change in internal energy of
the system?

A 20.0-L volume of an ideal gas in a cylinder with a piston is at a
pressure of 3.0 atm. Enough weight is suddenly removed from
the piston to lower the external pressure to 1.5 atm. The gas
then expands at constant temperature until its pressure is
1.5 atm. Find w.

A gas is confined to a cylinder under constant atmospheric 
pressure, as illustrated in Figure 5.4. When 0.49 kJ of heat is 
added to the gas, it expands and does 214 J of work on the 
surroundings. What are the values of H and E for this 
process?

Assume that a particular reaction evolves 244 kJ of heat and that 35 kJ of PV work is gained by the system. What are the values of ∆E and ∆H for the system? For the surroundings?

How much work (in J) is required to expand the volume of a
pump from 0.0 L to 2.5 L against an external pressure of 1.1 atm?

Consider a process in which an ideal gas changes from state 1 to state 2 in such a way that its temperature changes from 300 K to 200 K. (c) Does the change in the internal energy, ΔE, depend on the particular pathway taken to carry out this change of state?

The air in an inflated balloon (defined as the system) warms over
a toaster and absorbs 115 J of heat. As it expands, it does 77 kJ of
work. What is the change in internal energy for the system?

Enthalpy H and Internal Energy U

Internal Energy | 9-1 GCSE Physics | OCR, AQA, Edexcel

Which statement is true of the internal energy of a system and its
surroundings during an energy exchange with a negative ΔEsys?
a. The internal energy of the system increases and the internal
energy of the surroundings decreases.
b. The internal energy of both the system and the surroundings
increases.
c. The internal energy of both the system and the surroundings
decreases.
d. The internal energy of the system decreases and the internal
energy of the surroundings increases.

Internal Energy Example 1

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Professor Dave Explains

1. Intro to General Chemistry

2. Atoms & Elements

3. Chemical Reactions

4. BONUS: Lab Techniques and Procedures

5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

7. Gases

9. Quantum Mechanics

10. Periodic Properties of the Elements

11. Bonding & Molecular Structure

12. Molecular Shapes & Valence Bond Theory

13. Liquids, Solids & Intermolecular Forces

14. Solutions

15. Chemical Kinetics

16. Chemical Equilibrium

17. Acid and Base Equilibrium

18. Aqueous Equilibrium

19. Chemical Thermodynamics

20. Electrochemistry

21. Nuclear Chemistry

22. Organic Chemistry

23. Chemistry of the Nonmetals

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.

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

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;