Question

Write the formula for each of the following substances, listing the elements in the order given. a. a molecule containing three carbon atoms and eight hydrogen atoms b. a compound containing two nitrogen atoms for every oxygen atom c. a compound containing half as many barium atoms as iodine atoms d. a compound containing aluminum atoms and also three times as many chlorine atoms as there are aluminum atoms e. a sugar whose molecules contain 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms f. a compound that contains twice as many potassium atoms as carbon atoms, and three times as many oxygen atoms as carbon atoms

Short answer

a. C3H8 b. N2O c. BaI2 d. AlCl3 e. C12H22O11 f. K2CO3

Step-by-step solution

a. Molecule containing three carbon atoms and eight hydrogen atoms

The molecular formula for this substance is C3H8, as it contains three carbon atoms and eight hydrogen atoms.

b. Compound containing two nitrogen atoms for every oxygen atom

If the given compound contains two nitrogen atoms for every oxygen atoms, then it is like this: 2(N) : 1(O) So, the empirical formula of the compound is N2O.

c. Compound containing half as many barium atoms as iodine atoms

Let's represent the number of Iodine atoms with "x". Then, the number of Barium atoms would be (1/2)x. The formula for this compound is: Ba(1/2x)I(x) Simplifying this, we get: BaI2

d. Compound containing aluminum atoms and 3 times as many chlorine atoms as aluminum atoms

If the given compound contains aluminum atoms and three times as many chlorine atoms as aluminum atoms, the formula looks like: Al(1x)Cl(3x) Simplifying this, we get: AlCl3

e. Sugar containing 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms

The molecular formula for this sugar molecule is: C12H22O11

f. Compound containing twice as many potassium atoms as carbon atoms and three times as many oxygen atoms as carbon atoms

Assume x be the number of carbon atoms. By the condition given in the problem, the number of potassium atoms is 2x and the number of oxygen atoms is 3x. The formula for this compound is: K(2x)C(x)O(3x) Simplifying this, we get: K2CO3

Key concepts

Molecular Formula

The molecular formula of a compound reveals the exact number and type of atoms present within a molecule. It's like having a blueprint that shows you what building blocks are comprised in the molecular structure. This is distinct because it includes every atom type and its quantity in the compound.
For instance, consider a sugar molecule with the formula \( C_{12}H_{22}O_{11} \). This formula tells us exactly how many atoms of carbon, hydrogen, and oxygen are present. Yet, it's crucial to recognize that the molecular formula doesn't shed light on how these atoms are liked or arranged.

• It's essential for identifying specific compounds, particularly when isomeric substances share the same types and numbers of atoms but differ in arrangements.
• Molecular formulas are often used in chemical reactions to determine the proportions of reactants and products.

When you see a molecular formula, think of it as a detailed ingredient list needed to recreate a specific chemical structure.

Empirical Formula

An empirical formula is a simplified version of the molecular formula. It shows the simplest whole-number ratio of atoms within a compound without revealing the actual number of atoms. It's like the shorthand version of the formula.
For example, looking at the compound \( N_2O \), we see two nitrogen atoms for every one oxygen atom. This is derived from a compound where this ratio is constant, giving us the simplest expression of composition.

• Empirical formulas are particularly useful for understanding the basic quantitative relationships in compounds.
• They are often the first step in identifying unknown substances with techniques like combustion analysis.

In summary, while an empirical formula is a great tool for determining the elemental makeup, it doesn't provide the full picture of their arrangement or quantity in larger molecules.

Compound Composition

Compound composition refers to the ratio of different types of atoms in a compound. It tells us the relative proportions of each element in a chemical substance. Understanding the composition is key to predicting how a compound behaves and reacts with others.
For instance, let's consider a compound with the formula \( BaI_2 \). This indicates that for every barium atom, there are two iodine atoms. Identifying such ratios helps chemists understand the stability and reactions of compounds.

• Knowing compound composition aids in calculating molar masses and expected properties such as boiling points or solubility.
• It also assists in quantitative analyses, such as determining percentages of each element within a compound.

Think of compound composition as a recipe card showing what you need and in what quantities—it provides insights into how the compound's characteristics arise from its structure.

Chemical Structure

Chemical structure reveals the arrangement and connectivity of atoms within a molecule. It answers "where are the atoms located?" and "how do they bond?" This goes beyond what molecular or empirical formulas can tell us, providing a three-dimensional picture of the molecule.
Consider the structure of \( AlCl_3 \). While the empirical formula tells us there are three chlorines for every aluminum, the chemical structure will show us that aluminum is centrally bonded to three chlorine atoms. This structural information is crucial for understanding properties like reactivity and polarity.

• Chemical structure elucidates how molecules interact, influencing physical properties and chemical behavior.
• It's central to fields such as pharmacology, where a drug's efficacy depends on its structure.

Visualizing the chemical structure helps in understanding how specific arrangements affect the compound's stability and interactions, much like knowing the floor plan of a building enhances your understanding of its use.