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# A salt on reaction with dil. $H_2SO_4$ gives a reddish brown gas. The salt is

(a) $KNO_2$
(b) $ZnBr$
(c) $NaNO_3$
(d) $ZnCO_3$

Answer: $KNO_2$

$2KNO_2 + H_2SO_4 \longrightarrow K_2SO_4 + HNO_2$
$3HNO_2 \longrightarrow HNO_3 +H_2O + 2NO$
$2NO + O_2$ (from air) $\longrightarrow 2NO_3 \uparrow$ (reddish brown)
edited Jan 26, 2014