3. Amphoteric hydroxides a) Take 5-6 drops of a solution of any chromium (III) salt and add dropwise a diluted . solution of sodium hydroxide until the precipitate of chromium hydroxide is formed. Divide the precipitate of Cr(OH)_(3) into two parts and dissolve them in NaOH and HCl respectively. __ Reaction equations (molecular and ionic-molecular __ b) Repeat the same experiment using any zinc salt. __ Reaction equations (molecular and ionic-molecular forms) __

a) When a solution of a chromium (III) salt is added to a diluted solution of sodium hydroxide, a precipitate of chromium hydroxide, Cr(OH)3, is formed. The reaction can be represented as follows:<br /><br />Molecular form: CrCl3 + 3NaOH → Cr(OH)3 + 3NaCl<br />Ionic-molecular form: Cr3+ + 3OH- → Cr(OH)3<br /><br />When the precipitate of Cr(OH)3 is dissolved in NaOH, the following reaction occurs:<br /><br />Molecular form: Cr(OH)3 + NaOH → Na[Cr(OH)4]<br />Ionic-molecular form: Cr(OH)3 + OH- → [Cr(OH)4]-<br /><br />When the precipitate of Cr(OH)3 is dissolved in HCl, the following reaction occurs:<br /><br />Molecular form: Cr(OH)3 + 3HCl → CrCl3 + 3H2O<br />Ionic-molecular form: Cr(OH)3 + 3H+ → Cr3+ + 3H2O<br /><br />b) When a zinc salt is added to a diluted solution of sodium hydroxide, a precipitate of zinc hydroxide, Zn(OH)2, is formed. The reaction can be represented as follows:<br /><br />Molecular form: ZnCl2 + 2NaOH → Zn(OH)2 + 2NaCl<br />Ionic-molecular form: Zn2+ + 2OH- → Zn(OH)2<br /><br />When the precipitate of Zn(OH)2 is dissolved in NaOH, the following reaction occurs:<br /><br />Molecular form: Zn(OH)2 + NaOH → Na2[Zn(OH)4]<br />Ionic-molecular form: Zn(OH)2 + 2OH- → [Zn(OH)4]2-<br /><br />When the precipitate of Zn(OH)2 is dissolved in HCl, the following reaction occurs:<br /><br />Molecular form: Zn(OH)2 + 2HCl → ZnCl2 + 2H2O<br />Ionic-molecular form: Zn(OH)2 + 2H+ → Zn2+ + 2H2O