Formic acid and acetic acid differ in which of the following?

Saponification of ethyl benzoate with caustic soda as alkali gives:

Which of the following is the strongest acid?

Carboxylic acids are more acidic than phenol and alcohol. The reason for this is ......

Consider the acidity of the following carboxylic acids:
$(I)$ $PhCOOH$
$(II)$ $o-NO_2C_6H_4COOH$
$(III)$ $p-NO_2C_6H_4COOH$
$(IV)$ $m-NO_2C_6H_4COOH$
Which of the following is the correct order of acidity?

The acid having the highest $pK_a$ value among the following is