Question

Write the formula for each of the following substances, listing the elements in the order given. a. a molecule containing six carbon atoms and six hydrogen atoms b. a molecule containing two nitrogen atoms and four oxygen atoms c. a compound containing half as many calcium atoms as chlorine atoms d. a compound containing one iron atom for every three bromine atoms e. a compound containing equal numbers of sodium and nitrogen atoms, but three times as many oxygen atoms as there are sodium atoms f. a compound containing three calcium atoms for every two nitrogen atoms

Short answer

a. \(C_6H_6\) b. \(N_2O_4\) c. \(CaCl_2\) d. \(FeBr_3\) e. \(NaNO_3\) f. \(Ca_3N_2\)

Step-by-step solution

a. Molecule containing six carbon atoms and six hydrogen atoms

For this molecule, we directly know the number of each element's atoms present. There are six carbon atoms (C) and six hydrogen atoms (H). To write the chemical formula, simply combine the number of atoms of each element with their respective symbols: \(C_6H_6\). The chemical formula for the given molecule is \(C_6H_6\).

b. Molecule containing two nitrogen atoms and four oxygen atoms

This molecule contains two nitrogen atoms (N) and four oxygen atoms (O). The chemical formula for this molecule will include the number of atoms of each element with their respective symbols, like so: \(N_2O_4\). The chemical formula for the given molecule is \(N_2O_4\).

c. Compound containing half as many calcium atoms as chlorine atoms

In this case, we are not given the direct number of atoms for each element. Instead, we can represent the ratio between the number of calcium (Ca) and chlorine (Cl) atoms: if there are \(2x\) chlorine atoms, then there are \(x\) calcium atoms. The chemical formula will be \(Ca_xCl_{2x}\). In the simplest whole number ratio, we can set \(x = 1\) to obtain \(CaCl_2\). This compound is commonly known as calcium chloride, and its chemical formula is \(CaCl_2\).

d. Compound containing one iron atom for every three bromine atoms

We are given the ratio of iron (Fe) to bromine (Br) atoms in this compound: one iron atom for every three bromine atoms. In other words, for every \(Fe\) atom, there are 3 \(Br\) atoms. The chemical formula for this compound can be written as \(FeBr_3\). This compound is commonly known as iron(III) bromide, and its chemical formula is \(FeBr_3\).

e. Compound containing equal numbers of sodium and nitrogen atoms, but three times as many oxygen atoms as sodium atoms.

This compound contains equal numbers of sodium (Na) and nitrogen (N) atoms, and three times as many oxygen (O) atoms as sodium atoms. Let's represent the number of sodium and nitrogen atoms with \(x\). Since there are three times as many oxygen atoms as sodium atoms, the number of oxygen atoms will be \(3x\). The chemical formula for this compound will be \(Na_xN_xO_{3x}\). In the simplest whole number ratio, we can set \(x = 1\) to obtain \(NaNO_3\). This compound is commonly known as sodium nitrate, and its chemical formula is \(NaNO_3\).

f. Compound containing three calcium atoms for every two nitrogen atoms

In this compound, there are three calcium (Ca) atoms for every two nitrogen (N) atoms. We can represent this ratio by setting \(3x\) as the number of calcium atoms and \(2x\) as the number of nitrogen atoms. The chemical formula for this compound will be \(Ca_{3x}N_{2x}\). In the simplest whole number ratio, we can set \(x = 1\) to obtain \(Ca_3N_2\). This compound is commonly known as calcium nitride, and its chemical formula is \(Ca_3N_2\).

Key concepts

Chemical Nomenclature

Understanding chemical nomenclature is essential to master chemistry. It is the standardized system for naming chemical substances. Each compound's name reflects its composition, and the formula gives specific details on the type and number of atoms present.

For example, in the chemical formula \(C_6H_6\), the letter 'C' represents carbon and 'H' represents hydrogen. The subscript numbers indicate there are six of each atom type. This compound is also known as benzene. The ability to read and write these formulas allows us to communicate the exact substances involved in chemical reactions. When we encounter a compound like \(CaCl_2\), we can name it calcium chloride, which reveals the elements involved and suggests its properties and uses in the real world.

Molecular Composition

Molecular composition is all about the elements a molecule is made of and how many atoms of each element are present. Understanding this composition is crucial for predicting the behavior of molecules during chemical reactions.

Take \(N_2O_4\) as an example. This notation immediately informs us that one molecule consists of two nitrogen atoms and four oxygen atoms. By knowing the elements and their amounts, we can anticipate properties like reactivity and bonding patterns. It's like knowing a recipe—just as cooks need the right ingredients in the right amounts, chemists need the correct molecular composition to understand a compound's potential reactions and uses.

Atomic Ratio in Compounds

The atomic ratio in compounds describes the proportion of one type of atom to another within a compound. This concept is vital for determining the empirical formula, which is the simplest whole-number ratio of atoms in the compound.

For instance, the compound \(FeBr_3\) has an atomic ratio of one iron atom to three bromine atoms. Significantly, ratios help us derive the empirical formula, even when the molecular formula, which shows the actual number of atoms in a molecule, may be more complex. The atomic ratios steer the stoichiometry of reactions, predicting the outcomes when different compounds are mixed under certain conditions.

Stoichiometry

Stoichiometry is a section of chemistry that involves calculating the amounts of reactants and products in chemical reactions. It's based on the conservation of mass and the principle that each element has a fixed atomic weight.

Understanding stoichiometry helps us convert grams to moles, predict product yields, and balance chemical equations. For example, in the formation of \(NaNO_3\), knowing the stoichiometry allows us to calculate how much \(Na\), \(N\), and \(O\) we need to start with, or how much \(NaNO_3\) we will end up with from given amounts of reactants. It's a fundamental skill in chemistry that enables scientists and students to accurately describe and control chemical processes.