Question

1. use the solubility rules to identify the precipitate in the reaction. aqueous solutions of potassium hydroxide and cobalt(iii) nitrate are mixed.

here are the solubility rules.

1. alkali metal (li⁺, na⁺, k⁺, etc) and ammonium (nh₄⁺) salts are generally soluble. exceptions include li₂co₃ and li₃po₄.
2. nitrate (no₃⁻) salts are generally soluble.
3. silver (ag⁺) and lead (pb²⁺) salts are generally insoluble.
4. halide (cl⁻, br⁻, and i⁻) salts are generally soluble. exceptions include pb²⁺, ag⁺, hg₂²⁺.
5. carbonate (co₃²⁻), phosphate (po₄³⁻), and hydroxide (oh⁻) salts are generally insoluble.
6. sulfate (so₄²⁻) salts are generally soluble. exceptions include caso₄, srso₄, baso₄, pbso₄, and ag₂so₄.

koh
kno₃
co(no₃)₃
co(oh)₃

Explanation:

Step1: Write the reaction equation

The reaction between potassium hydroxide ($\ce{KOH}$) and cobalt(III) nitrate ($\ce{Co(NO_{3})_{3}}$) is a double - displacement reaction. The chemical equation is: $\ce{3KOH(aq) + Co(NO_{3})_{3}(aq)\xlongequal{}Co(OH)_{3}(s) + 3KNO_{3}(aq)}$

Step2: Analyze solubility of products using solubility rules

• For $\ce{KNO_{3}}$: According to solubility rule 1 (alkali metal salts are generally soluble) and rule 2 (nitrate salts are generally soluble), $\ce{KNO_{3}}$ is soluble in water.
• For $\ce{Co(OH)_{3}}$: According to solubility rule 5, hydroxide ($\ce{OH^{-}}$) salts are generally insoluble. Cobalt(III) hydroxide does not fall into any of the exception categories for hydroxide salts, so it is insoluble and will form a precipitate.

• $\ce{KOH}$ and $\ce{Co(NO_{3})_{3}}$ are reactants and are in aqueous solution initially, so they are not precipitates.

Answer:

$\ce{Co(OH)_{3}}$