1) To write the chemical formula you need to count the number of each element and put it in the following order: CHONPS
10) CH3-CH2-CH2-CH2-CH2-CH2-CH3
There is seven carbons and 16 hydrogen atoms. So the chemical formula is C₇H₁₆.
It's an alkane, so the name is prefixed with the carbon number and ending with ane.
The name of the compound is heptane.
11) CH3-CH2-CH2-CH3
There is four carbons and 10 hydrogen atoms. So the chemical formula is C₄H₁₀.
It's also an alkane, so the name is prefixed with the carbon number and ending with ane.
The name of the compound is butane.
12) CH3-CH2-CH2-CH2-CH3
There is five carbons and 12 hydrogen atoms. The chemical formula is C₅H₁₂.
It's also an alkane, so the name is prefixed with the carbon number and ending with ane.
The name of the compound is pentane.