Question

Explain with the help of balanced equations, how precipitation reactions are used for identifying the positive radicals in three different salts, each having a different cation [positive ion].

Answer 1

Precipitation reactions are used to identify the positive ions from their colours.
\[\ce{CuSO4 + 2NaOH->Na2SO4 + \underset{\text{pale blue ppt.}}{Cu[OH]2 v}}\]
identified ion is \[\ce{Cu^2+}\]
\[\ce{FeCl3 + 3NaOH->3NaCl + \underset{\text{reddish brown ppt.}}{Fe[OH]3 v}}\]
identified ion is \[\ce{Fe^3+}\]
\[\ce{Pb[NO3] + 2NaOH->2NaNO3 + \underset{\text{chalky white ppt.}}{Pb[OH]2 v}}\]
identified ion is \[\ce{Pb^2+}\]