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p Block Elements

Section: Chemistry

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Question : 61 of 62

Marks: +1, -0

A solution of colourless salt H on boiling with excess NaOH produces a non-flammable gas. The gas evolution ceases after sometime. Upon addition of Zn dust to the same solution, the gas evolution restarts. The colourless salt(s) H is(are)

[JEE Adv 2008 P1]

$NH_4NO_3$
$NH_4NO_2$
$NH_4Cl$
$(NH_4)_2SO_4$

Solution:

The colourless salt here can be

NH_4NO_3

or

NH_4NO_2

and the non-inflammable gas is

NH_3

and on addition of zinc dust, the evolution of ammonia again starts. The reactions involved are as follows:

NH_4NO_3

+ NaOH →

NH_3+NaNO_3+H_2O

7NaOH +

NaNO_3

+ 4Zn →

4Na_2ZnO_2 + NH_3+2H_2O

NH_4NO_2

+ NaOH →

NaNO_2 + NH_3+H_2O

3Zn + 5NaOH +

NaNO_2

→

3Na_2ZnO_2 + NH_3+H_2O

P_4

+ 3NaOH +

3H_2O

→

3NaH_2PO_2 + PH_3

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