When a mixture containing cations of Analytical Groups I–III is treated with H2S in acidic solution, which cations are expected to precipitate? Analytical Groups I and II Analytical Group I only Analytical Group III only Analytical Groups II and III Analytical Group II only

Analytical Groups I and II

Explanation:

Precipitation reactions happen when anions and cations in aqueous solution mix together to form an insoluble ionic solid which is now referred to as a precipitate.

Whether or not a type of reaction like that takes place can be determined by utilizing the solubility principles for common ionic solids.

Option D is the answer :

Analytical Groups II and III

Explanation:

Group II (Cu2+, Bi3+, Cd2+, Hg2+, As3+, Sb3+, Sn4+) cations produce very insoluble sulfides

(Ksp values less than 10-30) so they can be precipitated by low amounts of sulfide ion; this can be

achieved by adding an acidic solution of H2S.

Group III (Al3+, Cr3+, Fe3+, Zn2+, Ni2+, Co2+, Mn2+) cations produce slightly soluble sulfides

(Ksp values more than 10-20) so they can be precipitated by relatively high amounts of sulfide ion;

this can be achieved by adding a basic solution of H2S

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

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