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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)) ` ?A. `pH_(1)gt pH_(2)~~pH_(3)gt pH_(4)`B. `pH_(1)lt pH_(2)lt pH_(3) lt pH_(4)`C. `pH_(1)lt pH_(2)lt pH_(3)~~ pH_(4)`D. `pH_(1)gt pH_(2)gt pH_(3)gtpH_(4)` |
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Answer» Correct Answer - D The correct order of pH of isomolar solution of sodium oxide `(pH_(1))`, sodium sulphide `(pH_(2))`, sodium selenide `(pH_(3))` and sodium telluride `(pH_(4))` is `pH_(1)gt pH_(2)gt pH_(3)gt pH_(4)` because in aqueous solution, they are hydrolysed as follows. `Na_(2)O+2H_(2)O rarr underset("Base")(2NaOH)+H_(2)O` `Na_(2)S+2H_(2)O rarr underset("Strong base")(2NaOH)+underset("Weak acid")(H_(2)Se)` `Na_(2)Te+2H_(2)O rarr underset("strong base")(2NaOH)+underset("Weak acid")(H_(2)Te)` On moving down the group acidic character of oxides increases. Order of acidic strength Order of acidic strength `H_(2)Te gt H_(2)Se gt H_(2)S gt H_(2)O` Order of neutralisation of NaOH `H_(2)Te gt H_(2)Se gt H_(2)S gt H_(2)O` Hence, their aqueous solution have the following order of basic character due to neutralisation of NaOH with `H_(2)O,H_(2)S,H_(2)Se` and `H_(2)Te`. (`because pH` of basic solution is higher than acidic or least basic solution) |
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