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+, hg2^2+.
5. carbonate (co3^2-), phosphate (po4^3-), and hydroxide (oh-) salts are generally insoluble.
6. sulfate (so4^2-) 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

When potassium hydroxide ($\ce{KOH}$) and cobalt(III) nitrate ($\ce{Co(NO_{3})_{3}}$) are mixed, the double - replacement reaction occurs: $\ce{3KOH(aq) + Co(NO_{3})_{3}(aq)\xlongequal{}3KNO_{3}(aq) + Co(OH)_{3}(s)}$ (we assume the precipitate is one of the products, and we will check solubility for each product).

Step2: Analyze solubility of $\ce{KNO_{3}}$

According to solubility rule 1 (alkali metal salts are generally soluble) and rule 2 (nitrate salts are generally soluble), $\ce{KNO_{3}}$ (containing $\ce{K^{+}}$ and $\ce{NO^{-}_{3}}$) is soluble in water.

Step3: Analyze solubility of $\ce{Co(OH)_{3}}$

$\ce{Co(OH)_{3}}$ is a hydroxide salt. According to solubility rule 5, hydroxide ($\ce{OH^{-}}$) salts are generally insoluble. Cobalt(III) ion ($\ce{Co^{3+}}$) does not fall into the exception categories for hydroxide solubility, so $\ce{Co(OH)_{3}}$ is insoluble and will form a precipitate.

Answer:

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