The first law of thermodynamics | Practice Problems, Examples & Solutions

Thermodynamic Systems

Biochemistry

How can you tell if the standard Gibbs free energy given for a reaction is for chemical standard states or biological standard states?

The Importance of Energy Changes and Electron Transfer in Metabolism

01:13

Fundamentals of Thermodynamics

Prove that a cyclic device that violates the Kelvin-Planck statement of the second law also violates the Clausius statement of the second law.

The Second Law of Thermodynamics

01:49

Fundamentals of Thermodynamics

In a complete cycle what is the net change in energy and in volume?

The First Law of Thermodynamics

Work Done During Volume

51 Practice Problems

02:21

Atkins' Physical Chemistry

Calculate the molar internal energy of carbon dioxide at $25^{\circ} \mathrm{C}$, taking into account its translational and rotational degrees of freedom.

The First Law

Internal energy

09:25

Fundamentals of Thermodynamics

Liquid water at $180^{\circ} \mathrm{C}$ and $2000 \mathrm{kPa}$ is throttled into a flash evaporator chamber having a pressure of $500 \mathrm{kPa}$. Neglect any change in the kinetic energy. What is the fraction of liquid and vapor in the chamber?

First Law Analysis for a Control Volume

03:48

Fundamentals of Thermodynamics

A cylinder has $0.1 \mathrm{kg}$ of air at $25^{\circ} \mathrm{C}, 200 \mathrm{kPa}$ with a 5-kg piston on top. A valve at the bottom is opened to let the air out, and the piston drops $0.25 \mathrm{m}$ toward the bottom. What is the work involved in this process? What happens to the energy?

First Law Analysis for a Control Volume

Paths Between Thermodynamic States

26 Practice Problems

00:21

Thermodynamics : An Engineering Approach

Why are the chilled water lines always wrapped with vapor barrier jackets?

Gas-Vapor Mixtures and Air-Conditioning

05:36

Thermodynamics : An Engineering Approach

Repeat Prob. $13-9$ by replacing $\mathrm{N}_{2}$ by $\mathrm{O}_{2}$.

Gas Mixture

00:15

Thermodynamics : An Engineering Approach

What is the difference between the specific humidity and the relative humidity?

Gas-Vapor Mixtures and Air-Conditioning

Internal Energy

93 Practice Problems

03:46

Chemistry and Chemical Reactivity

The value of $\Delta U$ for the decomposition of $7.647 \mathrm{g}$ of ammonium nitrate can be measured in a bomb calorimeter. The reaction that occurs is
\[
\mathrm{NH}_{4} \mathrm{NO}_{3}(\mathrm{s}) \rightarrow \mathrm{N}_{2} \mathrm{O}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})
\]
The temperature of the calorimeter, which contains $415 \mathrm{g}$ of water, increases from $18.90^{\circ} \mathrm{C}$ to $20.72^{\circ} \mathrm{C}$
The heat capacity of the bomb is $155 \mathrm{J} / \mathrm{K}$. What is the value of $\Delta U$ for this reaction, in $\mathrm{kJ} / \mathrm{mol}$ ? (IMAGE CANNOT COPY)

Principles of Chemical Reactivity: Energy and Chemical Reactions

01:08

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

For a reaction at constant pressure, the enthalpy change is $+30 \mathrm{kJ} .$ During the reaction, the system expands and does $25 \mathrm{kJ}$ of work. What is the change in internal energy for the reaction? (Section 13.5 )

Energy and thermochemistry

03:04

Physical Chemistry

Collagen is the most abundant protein in the mammalian body. It is a fibrous protein that serves to strengthen and support tissues. Suppose a collagen fiber can be stretched reversibly with a force constant of $k=10.0 \mathrm{N} \mathrm{m}^{-1}$ and that the force $\mathbf{F}$ (see Table 2.1 ) is given by $\mathbf{F}=\mathbf{k} \cdot \mathbf{l}$ When a collagen fiber is contracted reversibly, it absorbs heat $q_{\text {rev}}=0.050 \mathrm{J}$. Calculate the change in the Helmholtz energy $\Delta A$ as the fiber contracts isothermally from $l=0.20$ to $0.10 \mathrm{m}$ Calculate also the reversible work performed $w_{r e v}, \Delta S,$ and $\Delta U$ Assume that the temperature is constant at $T=310 .$ K.

Chemical Equilibrium

First Law of Thermodynamics

61 Practice Problems

00:50

Thermodynamics : An Engineering Approach

Baseboard heaters are basically electric resistance heaters and are frequently used in space heating. A home owner claims that her 5 -year-old baseboard heaters have a conversion efficiency of 100 percent. Is this claim in violation of any thermodynamic laws? Explain.

The Second Law of Thermodynamics

00:48

Thermodynamics : An Engineering Approach

Describe an imaginary process that satisfies the second law but violates the first law of thermodynamics.

The Second Law of Thermodynamics

00:16

Thermodynamics : An Engineering Approach

An office worker claims that a cup of cold coffee on his table warmed up to $80^{\circ} \mathrm{C}$ by picking up energy from the surrounding air, which is at $25^{\circ} \mathrm{C}$. Is there any truth to his claim? Does this process violate any thermodynamic laws?

Introduction and Basic Concepts

Kinds of Thermodynamic Processes

48 Practice Problems

06:22

Thermodynamics : An Engineering Approach

A gas mixture has the following composition on a mole basis: 60 percent $\mathrm{N}_{2}$ and 40 percent $\mathrm{CO}_{2}$. Determine the gravimetric analysis of the mixture, its molar mass, and gas constant.

Gas Mixture

06:03

Thermodynamics : An Engineering Approach

The composition of moist air is given on a molar basis to be 78 percent $\mathrm{N}_{2}, 20$ percent $\mathrm{O}_{2},$ and 2 percent water vapor. Determine the mass fractions of the constituents of air.

Gas Mixture

00:08

Thermodynamics : An Engineering Approach

What is the difference between dry air and atmospheric air?

Gas-Vapor Mixtures and Air-Conditioning

Internal Energy of an Ideal Gas

30 Practice Problems

01:49

Physical Chemistry

A 1.50 mole sample of an ideal gas at $28.5^{\circ} \mathrm{C}$ expands isothermally from an initial volume of $22.5 \mathrm{dm}^{3}$ to a final volume of $75.5 \mathrm{dm}^{3} .$ Calculate $w$ for this process
(a) for expansion against a constant external pressure of $1.00 \times 10^{5} \mathrm{Pa}$ and (b) for a reversible expansion.

Heat, Work, Internal Energy, Enthalpy, and the First Law of Thermodynamics

03:41

Physical Chemistry

A compressed cylinder of gas contains $2.74 \times 10^{3} \mathrm{g}$ of $\mathrm{N}_{2}$ gas at a pressure of $3.75 \times 10^{7} \mathrm{Pa}$ and a temperature of $18.7^{\circ} \mathrm{C} .$ What volume of gas has been released into the atmosphere if the final pressure in the cylinder is $1.80 \times 10^{5}$ Pa? Assume ideal behavior and that the gas temperature is unchanged.

Fundamental Concepts of Thermodynamics

00:38

21st Century Astronomy

Phases of the interstellar medium include (choose all that
apply
a. hot, low-density gas.
b. cold, high-density gas.
c. hot, high-density gas.
d. cold, low-density gas.

The Interstellar Medium and Star Formation

Adiabatic Processes for an Ideal Gas

24 Practice Problems

04:59

Physical Chemistry

The temperature of 1.75 moles of an ideal gas increases from $10.2^{\circ} \mathrm{C}$ to $48.6^{\circ} \mathrm{C}$ as the gas is compressed adiabatically. Calculate $q, w, \Delta U,$ and $\Delta H$ for this process, assuming that $C_{V, m}=3 R / 2$

Heat, Work, Internal Energy, Enthalpy, and the First Law of Thermodynamics

04:48

Physical Chemistry

A 3.75 mole sample of an ideal gas with $C_{V, m}=3 R / 2$ initially at a temperature $T_{i}=298 \mathrm{K}$ and $P_{i}=1.00$ bar is enclosed in an adiabatic piston and cylinder assembly. The gas is compressed by placing a $725 \mathrm{kg}$ mass on the piston of diameter $25.4 \mathrm{cm} .$ Calculate the work done in this process and the distance that the piston travels. Assume that the mass of the piston is negligible.

Heat, Work, Internal Energy, Enthalpy, and the First Law of Thermodynamics

06:25

Fundamentals of Thermodynamics

A small, high-speed turbine operating on compressed air produces a power output of $100 \mathrm{W}$. The inlet state is $400 \mathrm{kPa}, 50^{\circ} \mathrm{C}$, and the exit state is $150 \mathrm{kPa},-30^{\circ} \mathrm{C} .$ Assuming the velocities to be low and the process to be adiabatic, find the required mass flow rate of air through the turbine.

First Law Analysis for a Control Volume

Different process in Thermodynamics

4 Practice Problems

01:52

Chemistry The Science in Context

Are exothermic reactions spontaneous only at low temperature? Explain your answer.

Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

01:53

Chemistry

Define stability from both a kinetic and thermodynamic perspective. Give examples to show the differences in these concepts.

Chemical Kinetics

03:02

Chemistry

Are the following processes exothermic or endothermic?
a. When solid $\mathrm{KBr}$ is dissolved in water, the solution gets colder.
b. Natural gas $\left(\mathrm{CH}_{4}\right)$ is burned in a furnace.
c. When concentrated $\mathrm{H}_{2} \mathrm{SO}_{4}$ is added to water, the solution gets very hot.
d. Water is boiled in a teakettle.

Thermochemistry

Energy Transfer Mechanisms in Thermal Processes

8 Practice Problems

01:10

University Physics

When heat transfers into a system, is the energy stored as heat? Explain briefly.

Temperature and Heat

01:18

Physics: A Conceptual World View

Suppose a student was careless in re-creating Joule's experiment and allowed the masses to speed up quickly as they dropped toward the floor. If he equated the change in gravitational potential energy with the change in thermal energy, would he have found 1 calorie to be greater than or less than 4.2 joules? Explain.

Thermal Energy

02:35

Conceptual Physics

Is there a distinction between thermal energy and internal energy? Which term do physicists prefer?

Temperature, Heat, and Expansion