Final answer:
The compound with the empirical formula CH₂ is Ethene (C₂H₄), as it has the simplest whole-number ratio of 1:2 for carbon to hydrogen. Option 3 is correct.
Step-by-step explanation:
The compound with the empirical formula CH₂ is Ethene (C₂H₄). An empirical formula represents the simplest whole-number ratio of the elements in a compound. Ethene's molecular formula, which shows the actual number of atoms of each element in a molecule, is C₂H₄ and this reflects a real molecule of ethene.
However, because the ratio of carbon to hydrogen atoms in ethene is 1:2, its empirical formula is CH₂. None of the other options (methane, ethane, methanol) have this ratio. Methane's molecular and empirical formula is CH₄, ethane's molecular and empirical formula is C₂H₆, and methanol's molecular formula is CH₃OH, which also serves as its empirical formula.
An empirical formula is one that shows the lowest whole-number ratio of the elements in a compound. Ethene (C₂H₄) has an empirical formula of CH₂. The simplest ratio of carbon to hydrogen in ethene is 1:2.
Example: Methane (CH₄), ethane (C₂H₆), and propane (C₃H₈) are compounds with empirical formulas that match their molecular formulas. However, ethene has an empirical formula of CH₂ while its molecular formula is C₂H₄.