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The mole is the SI base unit designated for measuring the SI base quantity of 'amount of substance'.
Answer: True
Explanation: The mole is indeed the SI base unit for the quantity 'amount of substance', not 'mass'. Mass is measured in kilograms.
A mole is defined as the amount of substance containing precisely 6.02214076 × 10²³ elementary entities.
Answer: True
Explanation: This definition, established in the 2019 SI revision, fixes the numerical value of the Avogadro constant, thereby defining the mole by a specific count of entities.
A mole is capable of representing various elementary entities, including atoms, molecules, ions, ion pairs, and subatomic particles.
Answer: True
Explanation: The definition of an 'elementary entity' is broad, allowing the mole to be applied to any specified fundamental particle or group of particles.
The official SI symbol for the mole unit is 'mol', not 'M'.
Answer: False
Explanation: The symbol 'M' is often used to denote molarity (moles per liter), but the unit symbol for the mole itself is 'mol'.
The mole concept dictates that a mole of water (H₂O) contains the same number of entities as a mole of mercury (Hg).
Answer: True
Explanation: By definition, one mole of any substance contains Avogadro's number of elementary entities, regardless of the substance's chemical nature.
The mole is similar in concept to a 'dozen' or 'pair' as a grouping term, but it represents a vastly larger quantity of items.
Answer: False
Explanation: Analogies like 'dozen' or 'pair' illustrate the mole as a unit representing a specific, large quantity of items, but the mole represents an astronomically larger number of items.
What fundamental quantity does the mole measure within the International System of Units (SI)?
Answer: Amount of substance
Explanation: The mole is the SI base unit specifically designated for the measurement of the 'amount of substance'.
Which of the following serves as the most accurate analogy for understanding the concept of a mole?
Answer: A dozen eggs
Explanation: Analogies like 'a dozen' help illustrate the mole as a unit representing a specific, large quantity of items, rather than a measure of size or weight.
Which of the following can be considered an 'elementary entity' that a mole represents?
Answer: An ion
Explanation: Elementary entities can include atoms, molecules, ions, ion pairs, or other specified particles.
How does the mole concept apply to substances composed of atoms versus molecules?
Answer: The number of entities is the same, but the mass and volume of a mole differ.
Explanation: A mole always represents the same number of entities (Avogadro's number), but the molar mass and volume vary depending on the atomic or molecular mass and structure of the substance.
The Avogadro number and the Avogadro constant represent the same numerical value but differ in their associated units.
Answer: True
Explanation: The Avogadro number is a dimensionless count, while the Avogadro constant includes the unit of reciprocal mole (mol⁻¹).
The Avogadro constant's value, as determined by CODATA in 2010, was approximately 6.02214076 × 10²³ mol⁻¹.
Answer: True
Explanation: This value was the best experimental determination prior to the 2019 redefinition, which fixed this numerical value exactly.
What is the exact numerical value that defines one mole?
Answer: 6.02214076 × 10²³
Explanation: Since the 2019 SI redefinition, one mole is defined as containing exactly 6.02214076 × 10²³ elementary entities.
What term specifically refers to the number of particles contained within one mole?
Answer: Avogadro number
Explanation: The Avogadro number (N₀) is the count of elementary entities in one mole.
What is the standard symbol designated for the Avogadro number?
Answer: N₀
Explanation: The Avogadro number is conventionally symbolized as N₀.
How is the Avogadro constant (N<0xE2><0x82><0x90>) defined?
Answer: The number of particles per mole (mol⁻¹).
Explanation: The Avogadro constant is defined as the number of specified elementary entities per mole, with its exact value fixed at 6.02214076 × 10²³ mol⁻¹.
What is the unit associated with the Avogadro constant?
Answer: mol⁻¹
Explanation: The Avogadro constant (N<0xE2><0x82><0x90>) is defined as the number of entities per mole, hence its unit is reciprocal mole (mol⁻¹).
The term 'mole' was introduced into scientific literature by the German chemist Wilhelm Ostwald in the late 19th century.
Answer: True
Explanation: The term 'mole' was coined by Wilhelm Ostwald in 1894, derived from the German word for molecule.
The mole was officially recognized as an SI base unit in 1971, not 1894.
Answer: False
Explanation: The mole was established as the seventh SI base unit by the 14th General Conference on Weights and Measures (CGPM) in 1971.
The 2019 revision of the SI redefined the mole by fixing the numerical value of the Avogadro constant.
Answer: True
Explanation: This redefinition shifted the basis of the mole from a material constant (mass of carbon-12) to a fixed numerical value for the Avogadro constant.
The current definition of the mole is not tied to the mass of a specific isotope like carbon-12; this was the basis for the pre-2019 definition.
Answer: False
Explanation: Since the 2019 SI revision, the mole is defined by a fixed numerical value of the Avogadro constant, independent of the mass of any substance.
John Dalton's early system for atomic masses used hydrogen as the standard, assigning it a value of 1, not oxygen with a value of 100.
Answer: False
Explanation: While oxygen was later used as a standard by Berzelius (initially assigning it 100), Dalton's foundational system used hydrogen as the reference point with an atomic mass of 1.
The definition of the mole prior to 2019 was linked to the kilogram through the mass of carbon-12.
Answer: True
Explanation: Specifically, one mole was defined as the amount of substance containing as many elementary entities as there are atoms in exactly 12 grams of carbon-12.
Who introduced the term 'mole' into scientific literature?
Answer: Wilhelm Ostwald
Explanation: Wilhelm Ostwald coined the term 'mole' in 1894, deriving it from the German word 'Molekül' (molecule).
What was the definition of the mole prior to the 2019 SI revision?
Answer: The amount of substance containing as many atoms as there are in 12 grams of carbon-12.
Explanation: This definition linked the mole to the mass of a specific isotope, establishing that 12 grams of carbon-12 contained one mole of atoms.
How did the 2019 SI revision change the definition of the mole?
Answer: It fixed the numerical value of the Avogadro constant.
Explanation: The revision redefined the mole by assigning an exact numerical value to the Avogadro constant (6.02214076 × 10²³ mol⁻¹), thereby defining the mole by a fixed count of entities.
What was the significance of John Dalton's contribution regarding atomic weights?
Answer: He published one of the first tables of standard atomic weights using hydrogen as a reference.
Explanation: Dalton's work in the early 19th century established a system for relative atomic weights, using hydrogen as the baseline.
The immense quantity of entities within a mole is a practical necessity, arising from the microscopic scale of atoms and molecules, which requires aggregation into macroscopic, measurable samples.
Answer: True
Explanation: Atoms and molecules are too small to be counted individually in laboratory settings. The mole provides a bridge by representing a quantity large enough for practical measurement.
The mole is primarily used in chemistry to quantify the amount of substance, not to express the volume of solutions.
Answer: True
Explanation: The mole is the fundamental unit for the amount of substance. While related to concentration (molarity, which involves volume), its primary role is quantifying the number of entities.
The mole concept serves as a crucial bridge, connecting microscopic particle counts (atoms, molecules) with macroscopic laboratory measurements.
Answer: True
Explanation: It allows chemists to work with tangible quantities of substances by relating them to the vast number of constituent particles.
Molar concentration, or molarity, is measured in units of moles per liter (mol/L), not moles per kilogram.
Answer: False
Explanation: Molarity specifically refers to the amount of solute per unit volume of solution. Moles per kilogram (mol/kg) is the unit for molality.
The mole concept is essential for stoichiometry, enabling the quantitative calculation of reactants and products in chemical reactions.
Answer: True
Explanation: Stoichiometry relies on mole ratios derived from balanced chemical equations to predict reaction yields and reactant consumption.
Why is the number of entities in a mole so large?
Answer: Because atoms and molecules are microscopic and require a large aggregate for practical measurement.
Explanation: The microscopic nature of atoms and molecules necessitates a very large number to form a macroscopic sample that can be weighed or measured in a laboratory.
In chemistry, what is a primary application of the mole concept?
Answer: Quantifying reactants and products in chemical reactions.
Explanation: The mole is fundamental to stoichiometry, enabling calculations of amounts in chemical reactions.
Given the reaction 2 H₂ + O₂ → 2 H₂O, how many moles of hydrogen react with one mole of oxygen?
Answer: 2 moles
Explanation: The balanced chemical equation indicates a stoichiometric ratio of 2 moles of H₂ for every 1 mole of O₂.
What is molar concentration, commonly referred to as molarity?
Answer: The number of moles of solute per unit volume of solution.
Explanation: Molarity is defined as the amount of solute (in moles) divided by the volume of the solution (in liters).
What is the primary role of the mole in relating microscopic entities to macroscopic quantities?
Answer: It provides a bridge for counting large numbers of microscopic particles in measurable macroscopic terms.
Explanation: The mole acts as a conversion factor, allowing chemists to work with large, countable quantities of microscopic particles in practical laboratory measurements.
Mole Day is typically celebrated on October 23rd, not January 1st.
Answer: False
Explanation: Mole Day is an informal holiday observed by chemists, most commonly celebrated on October 23rd, referencing the Avogadro number's value (6.022 x 10²³).
The Karlsruhe Congress of 1860 was a pivotal event for establishing consensus among chemists regarding atomic masses.
Answer: True
Explanation: This congress played a significant role in standardizing atomic weights, building upon earlier work and influencing future chemical understanding.
A criticism sometimes raised is that the mole, representing a count of entities, could be considered a dimensionless quantity, questioning its status as a base unit.
Answer: True
Explanation: Some critics argue that since the mole counts entities, it is fundamentally dimensionless, similar to radians, and thus its status as a base unit is debatable.
What is Mole Day, and when is it typically celebrated?
Answer: An informal holiday for chemists on October 23rd.
Explanation: Mole Day is an informal observance among chemists, usually celebrated on October 23rd, referencing the Avogadro number (6.022 x 10²³).
Which of the following is a criticism sometimes raised regarding the mole as an SI unit?
Answer: The number of entities is a dimensionless quantity, questioning the need for a base unit.
Explanation: Some critics argue that since the mole counts entities, it is fundamentally dimensionless, similar to radians, and thus its status as a base unit is debatable.