When \( \mathrm{Cu^{2+}} \) ion is treated with \( \mathrm{KI} \), a white precipitate, \( X \) appears in solution. The solution is titrated with sodium thiosulphate, the compound \( Y \) is formed, \( X \) and \( Y \) respectively are:
\( X = \mathrm{CuI_2} \) \( Y = \mathrm{Na_2S_4O_6} \)
\( X = \mathrm{Cu_2I_2} \) \( Y = \mathrm{Na_2S_4O_5} \)
\( X = \mathrm{CuI_2} \) \( Y = \mathrm{Na_2S_2O_3} \)
\( X = \mathrm{Cu_2I_2} \) \( Y = \mathrm{Na_2S_4O_6} \)
