Question

two gases which react under relevant conditions to give a gas which turns a solution of pottasium mercuric iodide brown.

choose from below---------

ammonia, hydrogen chloride, sulphurdioxide, nitrogen, oxygen, hydrogen, nitric oxide, methane, ethane.

Answer 1

Potassium mercuric iodide solution is turned brown by ammonia gas. This is also called as Nessler's reagent test.
The equation is given as,
NH₄⁺ + 2[HgI₄]²⁻ + 4OH⁻ $\to$ HgO·Hg(NH₂)I $\downarrow$ (brown ppt) + 7I⁻ + 3H₂O