### Chemistry Practical

goals
water should be added drop wise to concentrated sulphuric acid.
$\underset{\text{colourless salt}}{[A]} \xrightarrow{KOH}\underset{\text{gas}}{[B]}$ (gives white fumes with HCl)
$\downarrow CaCl_2$
$\underset{\text{white ppt.}}{[C]} \xrightarrow[(purple)]{KMnO_4}$ colourless solution
A coloured compound (A) reacts with dilute $H_2SO_4$ to produce a colourless gas (B) and colourless solution (C). The reaction between (B) and the acidified $K_2Cr_2O_7$ solution produces a green solution and a slightly yellowish precipitate (D). The substance (D) burns in air to produce a gas (E) which also can change colour of $K_2Cr_2O_7$ solution.
A colored solution known to contain two metals ions was treated with excess cold sodium hydroxide solution. When filtered a whitish solid, slowly changing to brown, was retained on the filter paper and a colorless solution collected as the filtrate. Dropwise addition of hydrochloric acid to the filtrate produced a white precipitate which dissolves in excess acid. Treatment of the residue from the filter paper with a solution of a strong oxidiser produced a reddish-violet solution.
A colored solution known to contain two metals ions was treated with excess cold sodium hydroxide solution. When filtered a whitish solid, slowly changing to brown, was retained on the filter paper and a colorless solution collected as the filtrate. Dropwise addition of hydrochloric acid to the filtrate produced a white precipitate which dissolves in excess acid. Treatment of the residue from the filter paper with a solution of a strong oxidiser produced a reddish-violet solution.