Question

How many hydrogen atoms are in an alkane molecule with nine carbon atoms? How many are in an alkene with nine carbon atoms and one double bond?

Short answer

Hydrogen atoms in alkane molecule with 9 carbons = \(2*9+2 = 20\) #Step 2: Calculate the hydrogen atoms in an alkene molecule with nine carbon atoms and one double bond# #tag_title# Calculate the hydrogen atoms in an alkene molecule (C9 with one double bond) #tag_content# The general formula for an alkene molecule is C_nH_(2n). Therefore, we have to substitute n = 9 to get the number of hydrogen atoms in an alkene molecule with nine carbon atoms and one double bond: Hydrogen atoms in alkene molecule with 9 carbons and 1 double bond = \(2*9\) Hydrogen atoms in alkene molecule with 9 carbons and 1 double bond = \(18\) #Answer# In an alkane molecule with nine carbon atoms, there are \(20\) hydrogen atoms. In an alkene molecule with nine carbon atoms and one double bond, there are \(18\) hydrogen atoms.

Step-by-step solution

Calculate the hydrogen atoms in an alkane molecule (C9)

The general formula for an alkane molecule is C_nH_(2n+2). Therefore, we have to substitute n = 9 to get the number of hydrogen atoms in an alkane molecule with nine carbon atoms: Hydrogen atoms in alkane molecule with 9 carbons = \(2*9+2\)

Key concepts

Alkane Formula

Alkanes are a fundamental class of hydrocarbons in organic chemistry. They are saturated compounds, which means they only contain single bonds between carbon atoms. The general formula for alkanes is \(C_nH_{2n+2}\). This formula helps determine the number of hydrogen atoms in any given alkane, based on the number of carbon atoms (designated as \(n\)).
For example, if you have an alkane with 9 carbon atoms (\(n = 9\)), you can use the formula to find the hydrogen count:

• Substitute \(n = 9\) into the formula \(C_nH_{2n+2}\).
• Calculate: \(2 \times 9 + 2 = 20\).

Thus, an alkane with nine carbon atoms will have 20 hydrogen atoms. This method of calculation is consistent, regardless of the size of the alkane molecule.

Alkene Structure

Alkenes are another important class of hydrocarbons, distinct from alkanes due to their unsaturated nature. They contain at least one double bond between carbon atoms. This introduces different structural characteristics compared to alkanes.
The presence of a double bond means alkenes have fewer hydrogen atoms than their alkane counterparts. The simplest alkene has the formula \(C_nH_{2n}\). This indicates that for every double bond present, two fewer hydrogen atoms are in the molecule.
Understanding alkene structure is critical to predicting the physical and chemical behavior of these molecules. The presence of a double bond can lead to unique reactions, such as addition reactions, because of the availability of pi electrons in the double bond.

Carbon-Hydrogen Bonds

In both alkanes and alkenes, the carbon-hydrogen bond plays a significant role in defining the properties of these compounds. This single covalent bond forms when one electron from a carbon atom and one from a hydrogen atom pair up. It's a moderately strong bond that significantly contributes to the stability and structure of hydrocarbons.
The bond is a result of the overlap of the hydrogen 1s orbital with the carbon sp³ hybrid orbital (in alkanes) or sp² orbital (in alkenes). Despite the bond's relative strength, hydrocarbons will react under suitable conditions to form new substances.

• In alkanes, all carbon atoms are bonded to hydrogen atoms in the 2n+2 formation.
• In alkenes, there are fewer carbon-hydrogen bonds due to the presence of at least one double bond among carbon atoms.

Double Bonds

Double bonds are defining characteristics of alkenes and play a crucial role in organic chemistry reactions and mechanisms. A double bond consists of one sigma bond and one pi bond. The sigma bond arises from head-to-head orbital overlap, while the pi bond results from side-to-side orbital overlap.
Because of the pi bond's weaker nature compared to the sigma bond, double bonds create sites of reactivity in organic molecules. These are the areas where chemical reactions like electrophilic addition can occur.

• The presence of double bonds reduces the number of hydrogen atoms in alkenes.
• They also affect molecular geometry, often leading to undesaturation in the hydrocarbons.

Variations in double bonds can result in different isomers, a concept important in stereoisomerism and influencing the physical properties of organic compounds.