Which of the following is not a possible empirical formula? CH_(5) P_(2)O_(6) C_(5)H_(11) NO_(2)

The correct answer is $CH_{5}$.<br /><br />Explanation:<br />Empirical formulas represent the simplest whole-number ratio of atoms in a compound. Let's analyze each option:<br /><br />1. $CH_{5}$: This formula suggests a 1:5 ratio of carbon to hydrogen, which is not a common or stable empirical formula for any known compound. Empirical formulas are typically simplified to the smallest whole-number ratio, and this ratio cannot be simplified further.<br /><br />2. $P_{2}O_{6}$: This formula represents a 2:6 ratio of phosphorus to oxygen, which can be simplified to $PO_{3}$, making it empirical formula.<br /><br />3. $C_{5}H_{11}$: This formula represents a 5:11 ratio of carbon to hydrogen, which is already in its simplest form and is a valid empirical formula.<br /><br />4. $NO_{2}$: This formula represents a 1:2 ratio of nitrogen to oxygen, which is already in its simplest form and is a valid empirical formula.<br /><br />Therefore, the correct answer is $CH_{5}$, as it is not a possible empirical formula.