### Chemistry Practical

goals
Cork stopper are used as _____ in the chemistry laboratory.
Chlorine gas dissolves in water, forming a greenish solution called perchloric acid.
When $H_2S$ gas is passed through $HCl$ containing aqueous solution of $CuCl_2$, $HgCl_2$, $BiCl_2$, and $CoCl_2$, it does not precipitate out:
Hardness of water can be removed by :
Two drops of phenolphthalein solution was added to $40.0mL$ of an $HCl$ solution. This solution was titrated with $0.10M$ $NaOH$ solution. When $30.0mL$ of base had been added, part of the solution turned pink; but the colour disappeared upon mixing the solution. Addition of $NaOH$ solution was continued dropwise until one drop addition produced a lasting pink colour. At this point, the volume of base added was $32.56mL$. Calculate:
(i) The concentration of $HCl$ solutions
(ii) Concentration of $HCl$ in solution when $30.0mL$ base had been added.