Question

Based on the following word descriptions, write the formula for each of the indicated substances. a. a compound whose molecules contain twice as many oxygen atoms as carbon atoms b. a compound whose molecules contain an equal number of carbon and oxygen atoms c. a compound in which there is an equal number of calcium and carbon atoms, but there are three times as many atoms of oxygen as of the other two elements d. a compound whose molecules contain twice as many hydrogen atoms as sulfur atoms and four times as many oxygen atoms as sulfur atoms e. a compound in which there are twice as many chlorine atoms as barium atoms f. a compound in which there are three sulfur atoms for every two aluminum atoms

Short answer

The formulas for the compounds based on the provided descriptions are: a. CO_2 b. CO c. CaCO_3 d. H_2SO_4 e. BaCl_2 f. Al_2S_3

Step-by-step solution

a. Compound with twice as many oxygen atoms as carbon atoms.

Let "C" represent a carbon atom and "O" represent an oxygen atom. Since there are twice as many oxygen atoms as carbon atoms, the formula can be represented as: CO_2

b. Compound with an equal number of carbon and oxygen atoms.

As the number of carbon atoms and oxygen atoms are equal, we can represent this compound as: CO

c. Compound with an equal number of calcium and carbon atoms, and three times as many oxygen atoms as the other two elements combined.

Let "Ca" represent a calcium atom. As there is an equal number of calcium and carbon atoms and three times as many oxygen atoms as the other two elements combined, we can represent this compound as: CaCO_3

d. Compound with twice as many hydrogen atoms as sulfur atoms, and four times as many oxygen atoms as sulfur atoms.

Let "H" represent a hydrogen atom and "S" represent a sulfur atom. Since there are twice as many hydrogen atoms as sulfur atoms, and four times as many oxygen atoms as sulfur atoms, we can represent this compound as: H_2SO_4

e. Compound with twice as many chlorine atoms as barium atoms.

Let "Ba" represent a barium atom and "Cl" represent a chlorine atom. Since there are twice as many chlorine atoms as barium atoms, we can represent this compound as: BaCl_2

f. Compound with three sulfur atoms for every two aluminum atoms.

Let "Al" represent an aluminum atom. As there are three sulfur atoms for every two aluminum atoms, we can represent this compound as: Al_2S_3

Key concepts

Stoichiometry

Stoichiometry is a foundational concept in chemistry that deals with the quantities of substances involved in reactions. It's based on the principle of the conservation of mass, where the amount of each element must be the same before and after a chemical reaction. To make sense of stoichiometry, imagine it as a recipe: for a cake to be perfect, specific amounts of ingredients are mixed together. Similarly, chemical reactions require precise proportions of reactants to yield products.

For example, when writing chemical formulas based on stoichiometry, if a compound has twice as many oxygen atoms as carbon atoms, as in the exercise part (a), it's analogous to saying you need double the amount of flour compared to sugar in a recipe. This would lead you to a molecular formula like CO₂, indicating each molecule consists of one carbon atom and two oxygen atoms. Understanding the stoichiometric ratios allows us to construct the correct molecular formulas of compounds and helps predict the outcomes of chemical reactions.

Chemical Nomenclature

Chemical nomenclature is the systematic method for naming chemical substances and writing their formulas based on the composition and structure of molecules. It's like giving every compound its unique 'name tag' that describes its makeup. For students, mastering chemical nomenclature is crucial for communication within the scientific community. It helps articulate precisely what substances are involved in a chemical reaction or composition.

Using the guidelines provided by IUPAC (International Union of Pure and Applied Chemistry), compounds are named based on the elements they contain and the quantities of these elements. For instance, in our part (e), 'BaCl₂' refers to barium chloride, indicating the compound contains one barium atom and two chlorine atoms. For compounds like CO, CO₂, and CaCO₃, the nomenclature reveals not just their systematic names – carbon monoxide, carbon dioxide, and calcium carbonate, respectively – but also provides insight into their stoichiometric makeup.

Molecular Composition

The molecular composition of a substance tells us about the different elements present in a molecule and their ratios. It's like understanding the full list of ingredients behind a dish's flavor. Knowing the molecular composition is essential because it gives us detailed information about the properties of the substance and how it will behave under certain conditions.

In chemical formula writing, as seen in the textbook exercise, the molecular composition directly influences the formula. For the example given in part (d), 'H₂SO₄' tells us that the sulfuric acid molecule comprises two atoms of hydrogen, one atom of sulfur, and four atoms of oxygen. This not only informs us of the ingredients but dictates the proportion in which they are bonded. Understanding molecular composition aids in predicting chemical reactivity and stability, vital for applications ranging from medicine to environmental science.