Question

Draw the structure for a hydrocarbon that has a chain of six carbon atoms linked by single bonds. How many hydrogen atoms does the molecule have? What is the molecular formula for the compound?

Short answer

The molecule has 14 hydrogen atoms, and the molecular formula for the compound is \( C_6H_{14} \) .

Step-by-step solution

Draw the carbon chain

Draw a straight chain of six carbon atoms. Since they are linked by single bonds, represent each bond between the carbon atoms with a single line.

Add hydrogen atoms

Add hydrogen atoms such that each carbon atom forms four bonds. Carbon atoms in the middle of the chain will have two hydrogen atoms each, while the end carbon atoms will each have three hydrogen atoms.

Counting hydrogen atoms

Count the total number of hydrogen atoms added to the chain. The two end carbon atoms contribute a total of 6 hydrogens (3 each), and the four middle carbon atoms contribute 8 hydrogens (2 each), giving a total of 14 hydrogen atoms.

Determine the molecular formula

The molecular formula of the compound can be written based on the number of carbon and hydrogen atoms. Since there are six carbon atoms and 14 hydrogen atoms, the molecular formula is \( C_6H_{14} \).

Key concepts

Carbon Chain

Understanding hydrocarbon structures begins with the concept of the carbon chain, which is the backbone of these molecules. In its simplest form, a carbon chain is a series of carbon atoms linked together by chemical bonds. These chains can vary in length and shape, forming straight lines, branched formations, or even rings.

When drawing hydrocarbons, the carbon chains are depicted with each carbon atom represented as a corner or an end of a line. Single bonds connect the carbons in a saturated hydrocarbon, which means each carbon atom is bonded to four atoms in total. This means if they are bonded to one or two other carbon atoms, the rest of the bonds will be to hydrogen atoms. In an exercise where a hydrocarbon with a six-carbon chain is depicted, the line will show a linear arrangement of six carbons, straight like a horizontal stick.

Visualizing the chain helps students understand hydrocarbon skeletons and is a fundamental starting point for learning about organic structures. It fosters an understanding of more complex molecular shapes, as the chains can bend and branch to form an endless variety of carbon-based compounds.

Hydrogen Atoms in Hydrocarbons

Hydrogen atoms are essential building blocks in hydrocarbon compounds. Each carbon atom has the ability to form four bonds due to its valency. In saturated hydrocarbons, where single bonds connect all the carbons (alkanes), each carbon fills its remaining valences with hydrogen atoms.

In a simple exercise of drawing a hydrocarbon, once the carbon chain is sketched, the next step is to add hydrogen atoms to each carbon. Central carbons (not at the ends of the chain) will typically bond to two hydrogen atoms because they are already bonded to two neighboring carbons in the chain. However, the terminal carbon atoms at the ends of the chain often have three hydrogen atoms since they're only bonded to one other carbon atom.

This step is visually straightforward but conceptually important as it reinforces the tetravalent nature of carbon and shows why hydrocarbons are rich in hydrogen. Students become familiar with filling out carbon valencies, a skill that helps when progressing to more complex organic molecules.

Molecular Formula

The molecular formula is a significant piece of information that provides a simple and precise way to represent the composition of a substance. For hydrocarbons, the molecular formula indicates the number of carbon and hydrogen atoms present in the molecule.

To find the molecular formula, we count the number of carbon and hydrogen atoms once the complete structure is drawn. For instance, in a given exercise for a hydrocarbon with six carbons all in a chain, we might determine that there are 14 hydrogen atoms after filling out the valencies for carbon; thus, the molecular formula becomes \( C_6H_{14} \).

This concise notation tells us not only about the constituent elements but also the exact number of each type of atom, which is crucial for understanding the compound's properties. It's a key concept that enables students to communicate chemical information efficiently and forms a fundamental part of chemical literacy.