Question

1. the scheme below shows some reaction sequence starting with solid m.

solid mxrightarrow{h_{2}so_{4}(aq)}solution n + gas which burns
with a pop sound
few drops of
nh_{3}(aq)
excess nh_{3}(aq)
colourless
white ppt
solution q
(a) name solid m
(b) write the formula of complex ion present in solution q

Explanation:

• (a)
• When a solid reacts with \(H_2SO_4(aq)\) to produce a gas that burns with a “pop” sound (which is \(H_2\)), the solid is a metal.
• When the metal - sulfate solution (\(N\)) reacts with \(NH_3(aq)\) to form a white ppt that dissolves in excess \(NH_3(aq)\) to form a colourless solution (\(Q\)), the metal is zinc. So solid \(M\) is zinc.
• (b)
• The reaction of \(Zn^{2 + }\) (from \(ZnSO_4\) in solution \(N\)) with excess \(NH_3(aq)\) forms the complex ion \([Zn(NH_3)_4]^{2+}\).

Answer:

• (a) Zinc
• (b) \([Zn(NH_3)_4]^{2+}\)