Chemistry Chapter 9: Energy and Chemistry

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Questions and Answers

How much energy is transformed into work if 515 J of heat is added to a gas that does 218 J of work?

297 J (correct)

737 J

515 J

297 J (correct)

What does a negative value of change in energy indicate?

Energy is released (correct)

Energy is transformed

Energy is conserved

Energy is absorbed

What are the two forms of energy flow in a system?

Force and motion

Power and energy

Heat and work (correct)

Mass and velocity

According to the first law of thermodynamics, which statement is true?

Total energy in a closed system remains constant. Signup and view all the answers

What is meant by the term 'system' in the context of energy transformations?

The part of the universe being considered Signup and view all the answers

What happens during an energy transformation when heat flows into a system?

Some heat is always lost to the surroundings. Signup and view all the answers

If the change in energy of a system is represented as DE, how is it calculated?

DE = q + w Signup and view all the answers

What is indicated when the sum of energy conversions and transfers equals the total energy present?

Energy conservation principle is upheld. Signup and view all the answers

What is waste energy primarily associated with in thermal systems?

Heat not converted to work Signup and view all the answers

What is the relationship between kinetic energy and motion?

Kinetic energy increases with increased speed. Signup and view all the answers

What does thermal pollution indicate?

Temperature changes due to waste streams Signup and view all the answers

Which factors determine the amount of heat a system can absorb?

Mass, specific heat capacity, and temperature change Signup and view all the answers

Which of the following correctly describes heat?

Heat is the transfer of energy due to a temperature difference. Signup and view all the answers

What does specific heat capacity measure?

Heat required to raise the temperature of one gram by 1ºC Signup and view all the answers

What is a primary characteristic of potential energy?

It is related to an object's position. Signup and view all the answers

What does the Joule measure in the SI unit system?

Energy. Signup and view all the answers

Which of the following statements is true regarding the molar heat capacity (Cp)?

It describes the heat needed to raise the temperature of one mole at constant pressure Signup and view all the answers

Which of the following energy types is released or absorbed during a chemical reaction?

Chemical energy Signup and view all the answers

Why are predicted efficiency gains for technologies important?

They can lead to reduced energy costs and consumption Signup and view all the answers

In calorimetry, what is the primary goal?

To observe and measure heat flow into and out of a system Signup and view all the answers

Which statement accurately describes work in a scientific context?

Work is performed when a force moves a mass across a distance. Signup and view all the answers

What role does mass play in heat absorption?

Increased mass results in higher heat requirements for temperature changes Signup and view all the answers

What is thermochemistry primarily concerned with?

Energetic consequences of chemical reactions. Signup and view all the answers

In the energy units, how is a Btu defined?

Energy required to raise 1 lb of water by 1°F. Signup and view all the answers

What does the variable 'q' represent in the context of calorimetry?

Heat energy Signup and view all the answers

In the formula $q = mc\Delta T$, what does the symbol 'm' refer to?

Mass of the substance Signup and view all the answers

How is the amount of heat gained by a system related to the heat lost by its surroundings?

They are equal. Signup and view all the answers

If 37.5 g of water is cooled from 42.0°C to 7.0°C, which formula would you use to calculate 'q' for the water?

$q = mc\Delta T$ Signup and view all the answers

What is the specific heat of gold based on the provided data?

0.129 J g-1 °C-1 Signup and view all the answers

What does the calorimeter constant, $C_{calorimeter}$, represent?

The heat capacity of the calorimeter Signup and view all the answers

In an actual measurement step of calorimetry, which variable is determined by the temperature change of the calorimeter?

Heat released by the reaction Signup and view all the answers

If a calorimeter measures a temperature change of 10°C and the calorimeter constant is 15 J/°C, what is the total heat exchanged?

150 J Signup and view all the answers

What percentage of energy consumption was used for residential purposes in the United States in 2011?

22% Signup and view all the answers

Which of the following forms of energy had the largest share in the total energy supply for the United States in 2011?

Natural gas Signup and view all the answers

What does the term 'conversion losses' refer to in the context of energy production?

Inefficiencies during electricity generation Signup and view all the answers

In what year was the total energy supply for the United States reported as 107.66 quadrillion Btu?

2011 Signup and view all the answers

What is the relationship between a nation's energy consumption and its economic growth?

Direct relationship Signup and view all the answers

What was the percentage of energy consumption attributed to the industrial sector in the United States in 2011?

31% Signup and view all the answers

Which statement best describes the function of state functions in thermodynamics?

They only depend on the current state of the system Signup and view all the answers

What approximate fraction of energy consumed to generate electricity accounts for conversion losses?

Two-thirds Signup and view all the answers

Study Notes

Chapter Objectives

Understand energy conversions, their economic importance, and associated losses.
Define work and heat utilizing standard sign conventions.
Explain state functions and their significance in thermodynamics.
Articulate the first law of thermodynamics both in words and as an equation.
Utilize calorimetric data to calculate changes in energy (ΔE) and enthalpy (ΔH) for chemical processes.
Define standard enthalpy of formation (ΔHf°) and construct formation reactions for compounds.
Summarize and apply Hess’s Law.

Energy Use and the World Economy

Energy consumption reflects a nation’s economic growth; correlated with Gross Domestic Product (GDP).
In 2011, the U.S. energy supply totaled 107.66 quadrillion Btu, with domestic production at 70.47 quadrillion Btu and imports at 31.02 quadrillion Btu.
Major energy sources in the U.S. include coal, natural gas, crude oil, NGPL, nuclear, and renewable energies.
Energy consumption distribution: Residential (22%), Commercial (19%), Industrial (31%), Transportation (28%).
Nearly half of domestic energy goes to electricity production, experiencing significant conversion losses.

Forms of Energy

Two primary types of energy:
- Potential Energy: Related to an object's position.
- Kinetic Energy: Associated with motion, calculated as KE = mv².
Internal Energy: Sum of kinetic and potential energy of atoms/molecules.
Chemical Energy: Energy change during chemical reactions; includes various forms: radiant, mechanical, thermal, electrical, and nuclear.

Heat and Work

Heat signifies energy flow due to temperature difference, flowing from warmer to cooler objects.
Work involves energy transfer through force moving a mass against resistance, commonly represented as pressure-volume work in chemistry.
Example of PV-work: Releasing air from an inflated balloon.

Energy Units

The Joule (J) is the SI unit of energy, equated as 1 J = 1 kg m²/s².
Other units include:
- Btu: Energy to raise 1 lb of water by 1°F, equivalent to 1055 J.
- Calorie: Energy to raise 1 g of water by 1°C, equivalent to 4.184 J.

Energy Transformation and Conservation

Energy transformation must conserve total energy, ensuring energy conversions equal the total present energy.
Defined system and surroundings play a role in energy flow, with boundaries separating them.
Energy flow in a system can occur as heat (q) or work (w), expressed as ΔE = q + w.

First Law of Thermodynamics

States energy can transform forms but cannot be created or destroyed; ΔEuniverse = ΔEsurroundings + ΔEsystem = 0.

Waste Energy

Energy conversion is inefficient; not all heat converts to work, leading to waste energy and potential thermal pollution.
Thermal pollution occurs from temperature changes in bodies of water due to waste heat.

Heat Capacity and Calorimetry

Calorimetry measures heat flow into/out of systems, influenced by mass (m), type of material, and temperature change (ΔT).
Specific Heat Capacity (c): Amount of heat needed to raise 1 g of a substance by 1°C.
Molar Heat Capacity (Cp): Heat necessary to raise 1 mole of a substance by 1°C, specific to compound and phase.

Calorimetric Measurements

Heat absorbed/calculated using q = mcΔT or q = nCpΔT equations.
Using calorimetry, the system's heat flow equals the negative of surroundings: qsystem = - qsurroundings.
Calibration of calorimeter constants allows the assessment of heat release/absorption in reactions.

Example Problem Applications

Problems demonstrate calculations using heat, mass, specific heat capacities, and conversion equations relevant to calorimetry measurements and thermodynamic principles.

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Description

Explore the fundamental concepts of energy and its role in chemistry through Chapter 9 of Larry Brown and Tom Holme's text. This quiz covers the economic importance of energy conversions, work, heat, state functions, and the first law of thermodynamics. Test your understanding of these key principles in chemistry.