AIIMS 2012 Chemistry Question Paper for free online practice with solutions

The correct order of pH of isomolar solution in sodium oxide (pH10 sodium sulphide (pH2), sodium selenide (pH3) and sodium telluride (pH4) is pH1>pH2>pH3>pH4 because in aqueous solution, they are hydrolysed as follows

Order of neutralisation of NaOH
H2Te>H2Se>H2S>H2O
Order of acidic strength
H2Te>H2Se>H2S>H2O Hence, their aqueous solutions have the following order of basic character due to neutralisation of NaOH with H2O,H2S,H2Se and H2Te.
Na2O>Na2S>Na2Se>Na2Te
(∴ pH of basic solution is higher than acidic or least basic solution).