energy and chemical reactions

Question 1

What is the first law of thermodynamics?

Answer 1

Energy cannot be created or destroyed, only transformed from one form to another.

Question 2

True or False: Enthalpy is a measure of the total energy of a thermodynamic system.

Answer 2

True

Question 3

Fill in the blank: The symbol for enthalpy is ____.

Answer 3

H

Question 4

What is calorimetry?

Answer 4

Calorimetry is the measurement of heat changes in physical and chemical processes.

Question 5

What is the standard state condition for a substance?

Answer 5

The standard state condition is defined as 1 bar of pressure and a specified temperature, typically 25°C.

Question 6

Which unit is commonly used to express enthalpy changes?

Answer 6

Joules (J)

Question 7

What does a negative change in enthalpy (ΔH) indicate?

Answer 7

It indicates that the reaction is exothermic, releasing heat.

Question 8

In a calorimetry experiment, what is the purpose of a calorimeter?

Answer 8

A calorimeter measures the heat absorbed or released during a chemical reaction.

Question 9

Multiple Choice: Which of the following is a state function? A) Work B) Heat C) Enthalpy D) Temperature

Answer 9

C) Enthalpy

Question 10

What is the formula for calculating the heat absorbed or released during a process?

Answer 10

q = m × c × ΔT, where q is the heat, m is mass, c is specific heat capacity, and ΔT is the change in temperature.

Question 11

True or False: Heat and temperature are the same concepts.

Answer 11

False

Question 12

What is the difference between specific heat and molar heat capacity?

Answer 12

Specific heat is the heat capacity per unit mass, while molar heat capacity is the heat capacity per mole of a substance.

Question 13

Fill in the blank: The heat of formation (ΔHf) is the change in enthalpy when one mole of a compound is formed from its ____ elements.

Answer 13

constituent

Question 14

What does a positive change in enthalpy (ΔH) indicate?

Answer 14

It indicates that the reaction is endothermic, absorbing heat.

Question 15

What is Hess’s Law?

Answer 15

Hess’s Law states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps.

Question 16

Multiple Choice: Which of the following processes is exothermic? A) Melting ice B) Vaporization of water C) Combustion of fuel D) Photosynthesis

Answer 16

C) Combustion of fuel

Question 17

What is the heat capacity of a substance?

Answer 17

Heat capacity is the amount of heat required to change the temperature of a substance by one degree Celsius.

Question 18

True or False: In an isolated system, energy can be exchanged with the surroundings.

Answer 18

False

Question 19

Fill in the blank: The change in enthalpy at constant pressure is equal to the ____ of the system.

Answer 19

heat exchanged

Question 20

What is the role of a bomb calorimeter?

Answer 20

A bomb calorimeter measures the heat of combustion of a substance under constant volume.

Question 21

What is the significance of the Gibbs free energy?

Answer 21

Gibbs free energy indicates the spontaneity of a process; a negative ΔG suggests a spontaneous reaction.

Question 22

What is the relationship between enthalpy and internal energy?

Answer 22

Enthalpy (H) is related to internal energy (U) by the equation H = U + PV, where P is pressure and V is volume.

Question 23

Multiple Choice: Which term describes the heat required to raise the temperature of one gram of a substance by one degree Celsius? A) Specific heat B) Molar heat capacity C) Thermal energy D) Latent heat

Answer 23

A) Specific heat

Question 24

What is the enthalpy change for a reaction when it is reversed?

Answer 24

The enthalpy change for a reversed reaction is equal in magnitude but opposite in sign to that of the forward reaction.

Question 25

Fill in the blank: The heat of reaction can be measured using a ____ calorimeter.

Answer 25

simple

Question 26

What is electromagnetic radiation?

Answer 26

Electromagnetic radiation is a form of energy that travels through space at the speed of light in the form of waves.

Question 27

Who proposed the concept of quantization of energy?

Answer 27

Max Planck proposed the concept of quantization of energy.

Question 28

True or False: Electromagnetic radiation can exist in discrete packets of energy called photons.

Answer 28

True

Question 29

What is the equation that relates energy (E) of a photon to its frequency (ν)?

Answer 29

E = hν, where h is Planck's constant.

Question 30

Fill in the blank: Planck's constant (h) is approximately _____ J·s.

Answer 30

6.626 × 10^-34

Question 31

What is a photon?

Answer 31

A photon is a quantum of electromagnetic radiation, representing the smallest possible discrete unit of light.

Question 32

What did Albert Einstein contribute to the understanding of photons?

Answer 32

Albert Einstein proposed that light can be thought of as both a wave and a particle, introducing the concept of the photon.

Question 33

What is the relationship between wavelength (λ) and frequency (ν) in electromagnetic radiation?

Answer 33

The relationship is given by the equation c = λν, where c is the speed of light.

Question 34

What are atomic line spectra?

Answer 34

Atomic line spectra are the discrete lines of color emitted or absorbed by atoms as electrons transition between energy levels.

Question 35

True or False: Niels Bohr developed a model of the atom that explained atomic line spectra.

Answer 35

True

Question 36

What principle did Niels Bohr introduce in his model of the atom?

Answer 36

Niels Bohr introduced the principle that electrons occupy quantized energy levels.

Question 37

What is the formula for the energy difference between two energy levels in a hydrogen atom?

Answer 37

ΔE = -13.6 eV (1/n_final^2 - 1/n_initial^2)

Question 38

Fill in the blank: The visible light spectrum ranges from _____ nm to _____ nm.

Answer 38

380, 750

Question 39

What does the term 'quantum' refer to?

Answer 39

A quantum refers to the smallest discrete quantity of energy that can be emitted or absorbed.

Question 40

What effect did Planck's hypothesis have on the field of quantum mechanics?

Answer 40

Planck's hypothesis led to the development of quantum mechanics by introducing the idea of quantized energy levels.

Question 41

Which scientist is known for explaining the photoelectric effect using the concept of photons?

Answer 41

Albert Einstein is known for explaining the photoelectric effect using the concept of photons.

Question 42

What is the significance of Planck's constant in quantum mechanics?

Answer 42

Planck's constant is a fundamental constant that relates the energy of a photon to its frequency and is a key part of quantum theory.

Question 43

What phenomenon occurs when light passes through a prism?

Answer 43

Dispersion occurs when light passes through a prism, separating it into its constituent colors.

Question 44

True or False: The Bohr model accurately describes all atomic structures.

Answer 44

False

Question 45

What is the main limitation of the Bohr model of the atom?

Answer 45

The Bohr model cannot accurately describe atoms with more than one electron.

Question 46

What does the term 'quantum leap' refer to?

Answer 46

A quantum leap refers to the transition of an electron from one energy level to another within an atom.

Question 47

What is the significance of the Balmer series?

Answer 47

The Balmer series describes the wavelengths of light emitted by hydrogen when electrons transition to the second energy level.

Question 48

Fill in the blank: The speed of light (c) is approximately _____ m/s.

Answer 48

3.00 × 10^8

Question 49

What is the photoelectric effect?

Answer 49

The photoelectric effect is the emission of electrons from a material when it absorbs light.

Question 50

What did the discovery of the photoelectric effect demonstrate about light?

Answer 50

It demonstrated that light has particle-like properties and can transfer energy to electrons.

Question 51

What is the relationship between energy and wavelength of a photon?

Answer 51

Energy is inversely proportional to wavelength; as wavelength decreases, energy increases.