What will be the decreasing order of basic strength of the following conjugate bases? $$^-OH,\ R\bar{O},\ CH_3CO\bar{O},\ C\bar{l}$$

We need to arrange the conjugate bases $$^-OH, R\bar{O}, CH_3CO\bar{O}, C\bar{l}$$ in decreasing order of basic strength.

Key Principle: The stronger the conjugate acid, the weaker the conjugate base (and vice versa).

The conjugate acids are: $$H_2O$$ (of $$^-OH$$), $$ROH$$ (of $$R\bar{O}$$), $$CH_3COOH$$ (of $$CH_3CO\bar{O}$$), $$HCl$$ (of $$C\bar{l}$$).

Acid strength order: $$HCl > CH_3COOH > H_2O > ROH$$

Since stronger acid gives weaker conjugate base:

$$ R\bar{O} > ^-OH > CH_3CO\bar{O} > C\bar{l} $$

Explanation: $$RO^-$$ is the strongest base because its conjugate acid (ROH, an alcohol) is the weakest acid. $$Cl^-$$ is the weakest base because its conjugate acid (HCl) is a very strong acid, meaning $$Cl^-$$ has virtually no tendency to accept protons.

The correct answer is Option (1): $$R\bar{O} > ^-OH > CH_3CO\bar{O} > C\bar{l}$$.