In the following drawings, red and blue spheres represent atoms of different elements. Match the molecular pictures (a)–(c) with the following descriptions: (i) a pure substance consisting of a compound (ii) a pure substance consisting of an element (iii) a mixture of element
Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 44c
Give molecular formulas corresponding to each of the following ball-and-stick molecular representations (red = O, gray = C, blue = N, ivory = H). In writing the formula, list the elements in alphabetical order. (c) Acetic acid (vinegar)
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Identify the colors of the atoms in the ball-and-stick model: red for oxygen (O), gray for carbon (C), blue for nitrogen (N), and ivory for hydrogen (H).
Count the number of each type of atom in the acetic acid molecule. Typically, acetic acid has 2 carbon atoms, 4 hydrogen atoms, and 2 oxygen atoms.
Write the molecular formula by listing the elements in alphabetical order: C, H, and O.
Combine the counts of each atom type into the molecular formula format: C_xH_yO_z, where x, y, and z are the respective counts of carbon, hydrogen, and oxygen atoms.
Ensure the molecular formula reflects the correct number of each type of atom as observed in the ball-and-stick model.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Formula
A molecular formula represents the number and types of atoms in a molecule. It is expressed by listing the chemical symbols of the elements present, followed by subscripts indicating the number of each type of atom. For example, the molecular formula for acetic acid is C2H4O2, which shows it contains two carbon (C), four hydrogen (H), and two oxygen (O) atoms.
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Ball-and-Stick Model
A ball-and-stick model is a three-dimensional representation of a molecule, where balls represent atoms and sticks represent the bonds between them. This model helps visualize the spatial arrangement of atoms and the connectivity within the molecule. In the case of acetic acid, the model would show the arrangement of carbon, hydrogen, and oxygen atoms, aiding in understanding its structure.
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Bohr Model of the Atom
Elemental Symbol Order
When writing a molecular formula, elements are typically listed in a specific order, often based on alphabetical arrangement of their chemical symbols. This standardization helps in quickly identifying the composition of the molecule. For acetic acid, the correct order is C, H, and O, leading to the formula C2H4O2, which adheres to this alphabetical convention.
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Related Practice
Textbook Question
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Textbook Question
Give molecular formulas corresponding to each of the following ball-and-stick molecular representations (red = O, gray = C, blue = N, ivory = H). In writing the formula, list the elements in alphabetical order. (a) Alanine (an amino acid)
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Textbook Question
Give molecular formulas corresponding to each of the following ball-and-stick molecular representations (red = O, gray = C, blue = N, ivory = H). In writing the formula, list the elements in alphabetical order. (b) Ethylene glycol (automobile antifreeze)
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Textbook Question
How many elements are presently known? About how many occur naturally?
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Textbook Question
What are the molecular weights of the following pharmaceuticals? (a) C33H35FN2O5 (atorvastatin, lowers blood cholesterol)
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Open Question
Which element accounts for roughly 75% of the observed mass of the universe? Which four elements make up 95% of the mass of the human body?