Observe the following species: $AlCl_3, NH_3, H^{+}, Co^{3+}, OH^{-}, Mg^{2+}, BF_3, Cl^{-}$. How many Lewis acids are present in the above list?

On dissolving $1 \ mole$ of each of the following acids in $1 \ L$ of water,the acid which does not give a solution of strength $1 \ N$ is:

The first ionization constants ($pK_a$ values) for the following dicarboxylic acids are given:
Oxalic acid: $pK_1$
Malonic acid: $pK_2$
Heptanedioic acid: $pK_3$
Which of the following represents the incorrect order of their $pK_a$ values?

Four species are listed below:
$i. \, HCO_3^-$
$ii. \, H_3O^{+}$
$iii. \, HSO_4^-$
$iv. \, HSO_3F$
Which one of the following is the correct sequence of their acid strength?

Which of the following is not a protonic acid?

Among the following,the dissociation constant $(K_a)$ is highest for: