Chemistry Practical

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.