Problem 60 - Chemistry: An Atoms-Focused Approach

Question

A precipitate may appear when two completely clear aqueous solutions are mixed. What circumstances are responsible for this event?

Step-by-Step Solution

Answer

Answer: A precipitate forms when two clear aqueous solutions are mixed if the combination of ions in the solutions leads to the formation of an insoluble product as a result of a chemical reaction. Factors contributing to precipitate formation include solubility rules, concentration, temperature, and pH changes.

Step 1: Understanding precipitate formation

When two clear aqueous solutions are mixed, a precipitate may appear if the combination of ions in the solutions leads to the formation of an insoluble product. This process typically occurs as a result of a chemical reaction taking place between the ions present in the two original solutions.

Step 2: Identifying the key factors contributing to precipitate formation

There are several factors that contribute to the formation of a precipitate when clear aqueous solutions are mixed, including: 1. Solubility Rules: Certain combinations of ions produce insoluble compounds, leading to the formation of a precipitate. These solubility rules are based on empirical observations and allow us to predict whether a particular combination of ions will form a precipitate or not. 2. Concentration: The concentration of the ions in the solutions plays a crucial role in determining whether a precipitate will form. If the concentration of the ions is high enough to exceed the solubility of the insoluble compound, a precipitate will form. 3. Temperature: The solubility of some compounds is temperature-dependent. A precipitate may form if the temperature of the reaction is such that the solubility of the produced compound is decreased. 4. pH: Changes in pH can also lead to precipitate formation as some compounds may become more or less soluble depending on the pH of the solution.

Step 3: Explaining examples of precipitate formation

Here are some examples to illustrate the concept of precipitate formation: 1. Mixing silver nitrate (AgNO3) and sodium chloride (NaCl) solutions: In this case, silver nitrate and sodium chloride react to form insoluble silver chloride (AgCl) and sodium nitrate (NaNO3), which remains dissolved in the solution: AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq) The precipitate formed here is silver chloride (AgCl). 2. Mixing barium chloride (BaCl2) and sodium sulfate (Na2SO4) solutions: In this reaction, the resulting products are barium sulfate (BaSO4), which is insoluble and forms a precipitate, and sodium chloride (NaCl), which remains dissolved in the solution: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq) The precipitate formed here is barium sulfate (BaSO4). From the given examples, it can be concluded that a precipitate forms when two completely clear aqueous solutions are mixed if the chemical reaction taking place between the ions present in the solutions produces an insoluble compound.