What is the correct relationship between the pH of isomolar solutions of sodium oxide `(pH_(1))`, sodium sulphide `(pH_(2))`, sodium selenide `(pH_(3))~, and sodium telluride `(pH_(4))` ?

Options

A. `pH_(1) lt pH_(2) lt pH_(3) lt pH_(4)`
B. `pH_(1) gt pH_(2) gt pH_(3) gt pH_(4)`
C. `pH_(1) lt pH_(2) lt pH_(3)~~pH_(4)`
D. `pH_(1) gt pH_(2)~~pH_(3) gt pH_(4)`

Answer

B

Explanation

It is a case of anionic hydrolysis
`A^(2-)(aq.)+2H-OH(l)hArrH_(2)A(aq.)+2OH^(-)(aq.)`
Thus, the stronger the base, the greater the extent of hydrolysis and the higher the pH. Since the correct order of basic strength is
`O^(2-)gtS^(2-)gtSe^(2-)gtTe^(2-)`
the correct order of pH is
`pH_(1) gt pH_(2) gt pH_(3) gt pH_(4)`