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Question Video: Determining the Molecular Formula of a Hydrocarbon Given a Displayed Formula Chemistry

The diagram shows a common hydrocarbon. What is the molecular formula of this hydrocarbon?

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Video Transcript

The diagram shows a common hydrocarbon. What is the molecular formula of this hydrocarbon?

This question is asking us to identify the molecular formula of a hydrocarbon. First of all, a molecular formula is a chemical formula expressing the exact number and type of atoms of each element in a molecule. In order for us to determine the molecular formula of this hydrocarbon, we need to first count up the total number of carbon atoms and the total number of hydrogen atoms in the molecule. First, when looking at the center of the molecule, we see a chain of four carbon atoms connected by single bonds. Because this hydrocarbon contains only single covalent bonds between the carbon atoms, it’s classified as an alkane. The name of this alkane is butane. But- is a prefix used with hydrocarbons to indicate the presence of four carbon atoms. And -ane is the ending used to indicate that the hydrocarbon is an alkane.

Now, let’s count up the total number of hydrogen atoms in the molecule. Surrounding the four carbon atoms, there are a total of 10 hydrogen atoms. When creating the molecular formula for butane, we identify the number of carbon atoms first and the number of hydrogen atoms second. The molecular formula of butane is therefore C4H10, where each subscript represents the number of atoms of the element it follows in the formula.

In conclusion, the molecular formula for the hydrocarbon butane is C4H10.

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