Video Transcript
Fill in the blank. The number of carbon atoms in a cycloalkane containing 24 hydrogen atoms is blank.
Alkanes are saturated hydrocarbons that only contain single covalent bonds. The carbon atoms of an alkane may be bonded in straight chains or in cyclic ringlike structures. The general formula of a straight-chain alkane is C𝑛H2𝑛+2, where 𝑛 represents the number of carbon atoms. Cyclic alkanes have one additional carbon-carbon single bond compared to their straight-chain counterparts. As such, cyclic alkanes have two fewer hydrogen atoms than straight-chain alkanes with the same number of carbon atoms. So the general formula of a cyclic alkane is C𝑛H2𝑛.
The question asked us to determine the number of carbon atoms in a cycloalkane. We are told that this cycloalkane contains 24 hydrogen atoms. We know from the general formula that the number of hydrogen atoms in a cyclic alkane is equal to two times 𝑛, the number of carbon atoms. This means that we can set 24 equal to two times 𝑛 then divide both sides by two to determine that 𝑛, the number of carbon atoms, is 12. We can verify that this is correct by drawing a structure for this molecule, starting by joining 12 carbon atoms in a ringlike structure. We can complete the structure by single bonding each carbon atom to two hydrogen atoms so that each carbon atom in the structure has formed four total bonds. This confirms that a 12-carbon cycloalkane will contain 24 hydrogen atoms.
So to answer the question, we should fill in the blank with 12 carbon atoms, the number of carbon atoms in a cycloalkane that contains 24 hydrogen atoms.
