Ammonia gas dissolves in water to form $NH_4OH$. In this reaction,water acts as:

Which of the following is a Lewis acid but not a Bronsted acid?

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

Which one of the following statements is not correct?

The conjugate base of sulphuric acid is

Which one of the following is not an amphoteric substance?