Final answer:
K2CrO4 and Ba(NO3)2 are not solids in water because they are soluble according to solubility rules, which state that most compounds containing nitrate ions and potassium ions are soluble and will remain dissolved in water.
Step-by-step explanation:
We know that K2CrO4 (potassium chromate) and Ba(NO3)2 (barium nitrate) are not solids when dissolved in water because they are both soluble ionic compounds. Solubility rules are guidelines that help us predict whether a compound will dissolve in water to form a homogeneous solution or form a precipitate. For instance, most compounds containing the nitrate ion (NO3-) are soluble, so Ba(NO3)2 will dissolve. Likewise, most potassium compounds, including K2CrO4, are also soluble in water.
When performing a double-replacement reaction, the ions in the reactants switch places and form new compounds. For a solid precipitate to form from such a reaction, one of the products must be insoluble according to the solubility rules.
An example of a reaction leading to a precipitate is the reaction between BaCl2 (aq) and Na2SO4 (aq) to form BaSO4 (s), which is insoluble and precipitates out of the solution.