Ch.2 - Atoms, Molecules & Ions

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.2 - Atoms, Molecules & Ions

Problem 115

Chapter 2, Problem 115

Label the following statements as true or false. (a) The atomic weight and the atomic number of an element have the same numerical value. (b) The molar mass in grams for an element and the atomic weight have the same numerical value.

Name: Chemistry
Author: McMurry
ISBN: 9781292336145

Verified step by step guidance

Step 1: Understand the concept of atomic number and atomic weight. The atomic number is the number of protons in an atom's nucleus, while the atomic weight (or atomic mass) is the weighted average mass of an atom of an element based on the abundance of its isotopes.

Step 2: Analyze statement (a). Compare the definitions of atomic number and atomic weight. Consider whether it is possible for these two values to be numerically the same for any element.

Step 3: Understand the concept of molar mass. The molar mass of an element is the mass of one mole of its atoms, usually expressed in grams per mole (g/mol).

Step 4: Analyze statement (b). Compare the definitions of molar mass and atomic weight. Consider how the atomic weight of an element, expressed in atomic mass units (amu), relates to its molar mass in grams per mole.

Step 5: Conclude the truthfulness of each statement based on the analysis of the definitions and relationships between atomic number, atomic weight, and molar mass.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Weight vs. Atomic Number

The atomic weight of an element is the weighted average mass of its isotopes, measured in atomic mass units (amu), while the atomic number is the number of protons in the nucleus of an atom, which defines the element. These two values are not the same; for example, carbon has an atomic number of 6 but an atomic weight of approximately 12.01 amu.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For elements, the molar mass numerically equals the atomic weight in amu, meaning that the molar mass of an element in grams is the same as its atomic weight, allowing for direct conversion between the two units.

True/False Statements in Chemistry

In chemistry, evaluating statements as true or false often requires a clear understanding of definitions and relationships between concepts. For instance, recognizing that atomic weight and atomic number are distinct helps in determining the truth of statements regarding their numerical values, while understanding molar mass allows for accurate comparisons with atomic weight.

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Textbook Question

(a) The unified atomic mass unit (u) is used to represent the extremely small mass of atoms. How many grams are equivalent to 1 u?

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Textbook Question

Magnesium has three naturally occurring isotopes: ²⁴Mg (23.985) with 78.99% abundance, ²⁵Mg (24.986) with 10.00% abundance, and a third with 11.01% abundance. Look up the atomic weight of magnesium, and then calculate the mass of the third isotope.

Match the descriptions (a)–(e) with the following terms: atomic weight, atomic mass, mass number, atomic number, molar mass.(a) The mass of a specific atom such as one atom of 13C (b) The quantity determined by the number of protons in an element.(c) The number of grams in 1 mol of an element (d) The number of protons and neutrons in an element (e) The weighted average of the isotopic masses of an element's naturally occurring isotopes

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Textbook Question

(b) The mole is a unit used to represent a very large number of atoms. How many atoms are equivalent to 1 mol of atoms?

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Textbook Question

Naturally occurring silver consists of two isotopes: 107^Ag (51.84%) with an isotopic mass of 106.9051 and 109^Ag (48.16%) with an isotopic mass of 108.9048. What is the atomic weight of silver? Check your answer in a periodic table.

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