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JEE Main levelSingle correct optionDifficulty 2 of 3qa011

Which of the following ammonium salts leaves a non-volatile residue when heated strongly in a dry hard-glass tube?

A $NH X_{4} HCO X_{3}$
B $(NH X_{4}) X_{3} PO X_{4}$
C $(NH X_{4}) X_{2} CO X_{3}$
D $NH X_{4} Cl$

Answer: B

NH X_{4} Cl

dissociates to

NH X_{3}

and HCl and re-forms as a sublimate.

(NH X_{4}) X_{2} CO X_{3}

and

NH X_{4} HCO X_{3}

break down completely into

NH X_{3}

,

CO X_{2}

and

H X_{2} O

. Ammonium phosphate loses

NH X_{3}

and leaves non-volatile phosphoric acid (finally polyphosphoric or metaphosphoric acid) as residue.

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