Video Transcript
Fill in the blank: The number of
hydrogen atoms in an alkane containing two carbon atoms is blank.
In this question, we are being
asked to determine how many hydrogen atoms an alkane molecule would have if it
contained two carbon atoms. We will need to fill in the blank
in the statement with the correct number of hydrogen atoms. First of all, an alkane is a type
of molecule called a hydrocarbon. Hydrocarbons are composed only of
carbon and hydrogen. An alkane is further classified as
a saturated hydrocarbon. A saturated hydrocarbon contains
only single covalent bonds between the carbon atoms.
Since we know that each carbon atom
can form a total of four single bonds with other atoms, we can sketch out the
displayed formula of the molecule. Let’s start by connecting two
carbon atoms with a single bond. Next, we know that each carbon atom
can form an additional three single bonds with other atoms. These atoms will be hydrogen
atoms. In total, the alkane molecule will
contain two carbon atoms and six hydrogen atoms.
There is another very useful way to
quickly determine the number of hydrogen atoms in an alkane molecule. By definition, an alkane is a
saturated hydrocarbon with the general formula C𝑛H2𝑛+2. To use this formula, we will need
to replace 𝑛 with the number of carbon atoms in the molecule. In the problem, we were told that
the alkane contained two carbon atoms. So let’s substitute two for 𝑛 in
the formula. The result is C2H2(2)+2. After simplification, we get the
molecular formula C2H6. Each subscript in the molecular
formula represents the number of that type of atom in the molecule.
So, using the general formula for
an alkane, we’ve confirmed that the alkane contains two carbon atoms and six
hydrogen atoms. Therefore, the number of hydrogen
atoms in an alkane containing two carbon atoms is six hydrogen atoms.
