Question

0.98gm of the metal sulphate was dissolved in water and excess of barium chloride was added. The precipitated barium sulphate weighted 0.95gm. calculate the equivalent weight of the metal.

Answer 1

A chemical reaction occurring in an aqueous solution, the formation of insoluble salt due to the combination of two ions, that reactions are precipitation reactions. In these reactions, two soluble compounds combine to form one soluble and insoluble solid which is precipitated out. This insoluble solid is called a precipitate.

Complete step by step solution:
Precipitate reactions are carried out by various separating methods like filtration, centrifuging, or decanting and the same methods are used to separate precipitates from solution.
Such reaction is precipitation reaction or not determined by solubility rules for common ionic solids. These rules provide guidelines for which ions soluble or insoluble.
-Except for lithium ions from alkali metal, salts formed are soluble.
-Acetates, nitrates and perchlorates are soluble.
-All halides are soluble in aqueous solution.
-The salts which are formed from silver, mercury are insoluble.
-All sulfides are soluble, except calcium sulphate, barium sulphate and strontium sulphate.

In the given precipitation reaction, the insoluble salt is barium sulphate which is precipitated weighing 0.95g.
Weight of $BaS{{O}_{4}}$ = 0.95g
Molecular weight of $BaS{{O}_{4}}$= 233.42g
Constituent weight or Strength of sulphate = $=\dfrac{molecular\text{ }weight\text{ }of\text{ }sulphate}{Molecular\text{ }weight\text{ }ofBaS{{O}_{4}}}=\dfrac{96g}{233.42g}=41.1$
Weight of sulphate in 0.95g = $\dfrac{41.1X0.95}{100}=0.39$
The equivalent weight of metal = 0.98g-0.39g= 0.59g.

Hence, the equivalent weight of the metal is 0.59gm.

Note: Precipitates are also used for quantitative and qualitative analysis of solutions. Not all aqueous reactions are precipitation reactions, which obeys solubility rules before estimating the rate of products and net ionic equation. For example, silver nitrate, sodium chloride both are soluble solids, but when we add both salts silver chloride formed as white precipitation.