Question

Write the formulas for the compounds described by the following compositions. (a) twice as many hydrogen atoms as sulfur atoms (b) \(1.5\) times as many oxygen atoms as nitrogen atoms (c) one-half as many calcium ions as chloride ions

Short answer

Thus, the formulas for the compounds are: (a) \(H_2S\), (b) \(N_2O_3\), (c) \(CaCl_2\).

Step-by-step solution

Infer the Formula Based on Hydrogen and Sulfur Composition

In the first compound, for every one sulfur atom, there are twice as many hydrogen atoms. As a result, the molecular formula of the compound is \(H_2S\).

Write the Formula Based on Oxygen and Nitrogen Composition

The second compound has \(1.5\) or \(3/2\) times as many oxygen atoms as nitrogen atoms. However, chemical formulas need to be in the smallest whole numbers, so we double each to get rid of the \(0.5\). As a result, the molecular formula of this compound is \(N_2O_3\).

Determine the Formula Based on Calcium and Chloride Ions Composition

The third compound has one-half as many calcium ions as chloride ions. This means for every two chloride ions, there's one calcium ion. Hence, the formula of this compound is \(CaCl_2\).

Key concepts

Stoichiometry

Stoichiometry is the aspect of chemistry that deals with the quantitative relationships that govern the combination of elements in chemical reactions. Imagine it as a recipe: stoichiometry tells us how much of each ingredient we need to mix together to create a certain product. In the context of the exercises, stoichiometry is used to discern the proper ratios of atoms in a compound.
For example, part (a) of the given exercise requires understanding that if there are 'twice as many hydrogen atoms as sulfur atoms,' the ratio is 2:1. To solve such problems, a basic understanding of ratios and a grasp of how to convert between moles and numbers of atoms or molecules using Avogadro's number are essential. This allows students to determine the amounts of reactants needed or the amounts of products formed in a chemical reaction.

Practical Tip: Ratios and Balancing

When dealing with stoichiometry, always make sure your ratios of atoms or molecules are in the simplest whole numbers. If you encounter a fraction or a decimal, like in part (b), multiply all sides of the ratio by the smallest number that will convert all numbers into whole numbers. This maintains the balance needed in chemical equations and formulas.

Molecular Composition

Molecular composition refers to the types and numbers of atoms that constitute a molecule. Knowing the molecular composition is crucial for understanding the properties of the compound and how it interacts in chemical reactions. In the exercises, the molecular composition is directly related to the chemical formulas you are creating.
You have to first identify the elements involved and then use the given ratios to determine the numbers of each type of atom in the compound. The composition provides the backbone of the chemical formula—the script that chemists follow to know exactly what, and how much, each element is in a compound.

Connecting Composition to Real-World Applications

In real-world applications, such as the pharmaceutical industry, understanding molecular composition is imperative. For instance, changing a single atom in a medicinal compound can drastically alter its effectiveness or side effects. This emphasizes the importance of accurate molecular formulas derived from correct molecular compositions.

Chemical Nomenclature

Chemical nomenclature is the system of names that chemists use to identify and communicate about chemical substances. It involves a set of rules to generate systematic names for chemical compounds. In simpler terms, it's the language that scientists use to accurately describe and categorize chemicals.
In the given exercise, once we establish the correct formulas such as the sulfur and hydrogen compound being written as \(H_2S\), it is then named 'hydrogen sulfide' according to chemical nomenclature standards. Ionic compounds like calcium chloride, derived in part (c) as \(CaCl_2\), are named based on the cation (calcium) first, followed by the anion (chloride).

Importance of Correct Names

Understanding chemical nomenclature is vital because it allows clear and unambiguous communication between scientists. Without a consistent system, sharing findings, creating new compounds, or ordering substances from suppliers would be fraught with confusion and errors. Chemical nomenclature removes the ambiguity by providing a universal language that enables chemists from around the globe to work together effectively.