Question

How many hydrogen atoms would be present in alkane molecules with the indicated number of carbon atoms? a. eight b. sixteen c. one d. four

Short answer

a. For an alkane with eight carbon atoms, there would be 18 hydrogen atoms. b. For an alkane with sixteen carbon atoms, there would be 34 hydrogen atoms. c. For an alkane with one carbon atom, there would be 4 hydrogen atoms. d. For an alkane with four carbon atoms, there would be 10 hydrogen atoms.

Step-by-step solution

a. Eight carbon atoms in alkane molecule

Given that there are eight carbon atoms, we can substitute n = 8 in the general alkane formula, CnH2n+2: - Find the number of hydrogen atoms: H = 2(8) + 2 = 16 + 2 = 18 There would be 18 hydrogen atoms in an alkane with eight carbon atoms.

b. Sixteen carbon atoms in alkane molecule

Given that there are sixteen carbon atoms, we can substitute n = 16 in the general alkane formula, CnH2n+2: - Find the number of hydrogen atoms: H = 2(16) + 2 = 32 + 2 = 34 There would be 34 hydrogen atoms in an alkane with sixteen carbon atoms.

c. One carbon atom in alkane molecule

Given that there is one carbon atom, we can substitute n = 1 in the general alkane formula, CnH2n+2: - Find the number of hydrogen atoms: H = 2(1) + 2 = 2 + 2 = 4 There would be 4 hydrogen atoms in an alkane with one carbon atom.

d. Four carbon atoms in alkane molecule

Given that there are four carbon atoms, we can substitute n = 4 in the general alkane formula, CnH2n+2: - Find the number of hydrogen atoms: H = 2(4) + 2 = 8 + 2 = 10 There would be 10 hydrogen atoms in an alkane with four carbon atoms.

Key concepts

General Alkane Formula

The general formula for alkanes plays a crucial role in understanding how these organic molecules are structured. Alkanes, being the simplest type of hydrocarbons, consist solely of carbon and hydrogen atoms. The formula is represented as \( C_nH_{2n+2} \), where \( n \) stands for the number of carbon atoms.
To find the number of hydrogen atoms in an alkane, you simply need to double the carbon atoms and add two. For instance, if an alkane has eight carbon atoms, you use the formula: \( H = 2(8) + 2 \), resulting in 18 hydrogen atoms. This formula is a handy tool that helps predict the structure of alkanes regardless of how large or small the molecule is.
Understanding this formula allows students to identify the number of hydrogen atoms in any given alkane molecule efficiently.

• It highlights the simplicity and consistency in the way alkanes grow in size.
• This predictable pattern aids in learning more complex organic chemistry concepts later.

Hydrogen Atoms

In alkane molecules, hydrogen atoms surround the carbon chain to satisfy the valency of carbon. Carbon forms four bonds, so in alkanes, all carbon atoms are bonded as \(-CH_3\) or \(-CH_2-\) groups, ensuring all valencies are satisfied.
The count of hydrogen atoms in an alkane is dictated by the general alkane formula \( C_nH_{2n+2} \). It investigates how hydrogen atoms balance out the carbon skeleton:

• Hydrogen bonds to carbon to form single-bonded chains, which are the hallmark of alkanes.
• The addition of each carbon increases the molecule's size, but the number of hydrogen's grows predictably.

Understanding hydrogen atom configuration within alkanes provides a framework for recognizing more complex chemical reactions involving hydrocarbons.

Carbon Atoms

Carbon atoms are the backbone of organic chemistry and alkanes are no exception. In alkanes, the carbon atoms are saturated, which means they only form single bonds between each other.
Each carbon atom in an alkane is bonded in a tetrahedral geometry, with each carbon having four bonds - either to hydrogen or to another carbon. This provides a stable, flexible structure for the molecule.

• For example, methane, the simplest alkane, has one carbon atom bonded to four hydrogen atoms, forming \( CH_4 \).
• The pattern continues: ethane with two carbon atoms is \( C_2H_6 \).
• This predictability makes alkanes a foundational concept in studying larger organic molecules.

Grasping the role of carbon atoms in alkanes is essential for visualizing and understanding the bigger world of organic chemistry structures.

Organic Chemistry

Organic chemistry focuses on the study of carbon-containing compounds, including not just alkanes but a vast world of different molecular structures. Alkanes are often referred to as "saturated hydrocarbons" because they contain the maximum number of hydrogen atoms bonded to carbon.
Alkanes serve as a baseline for understanding more complex organic reactions and structures. Knowledge of their straightforward chemical behavior and stability is invaluable in countless real-world applications.

• They act as fuels (like in natural gas and petroleum).
• These hydrocarbons also form building blocks for producing plastics, lubricants, and other chemical products.

By examining alkanes, students pave their way to exploring more intricate organic systems, deepening their understanding of chemistry's role in everyday life.