Question

Will precipitation occur when the following solutions are mixed? If so, write a balanced chemical equation for the reaction. (a) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and \(\mathrm{AgNO}_{3},\) (b) \(\mathrm{NaNO}_{3,}\) and \(\mathrm{NiSO}_{4,}\) (c) \(\mathrm{FeSO}_{4}\) and \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}.\)

Short answer

(a) Yes, precipitation occurs. The balanced chemical equation is: \( 2\mathrm{AgNO}_{3}(aq) + \mathrm{Na}_{2}\mathrm{CO}_{3}(aq) \rightarrow \mathrm{Ag}_{2}\mathrm{CO}_{3}(s) + 2\mathrm{NaNO}_{3}(aq) \) (b) No precipitation occurs when NaNO3 and NiSO4 solutions are mixed. (c) Yes, precipitation occurs. The balanced chemical equation is: \( \mathrm{FeSO}_{4}(aq) + \mathrm{Pb(NO}_{3})_{2}(aq) \rightarrow \mathrm{PbSO}_{4}(s) + \mathrm{Fe(NO}_{3})_{2}(aq) \)

Step-by-step solution

(a) Mixing Na2CO3 and AgNO3 solutions

Step 1: Write the possible products' chemical formulas By mixing \(\mathrm{Na}_{2}\mathrm{CO}_{3}\) and \(\mathrm{AgNO}_{3}\) solutions, we can have the following possible products: Ag2CO3 and NaNO3 Step 2: Determine their solubility according to solubility rules Ag2CO3: Silver carbonate is generally insoluble in water. NaNO3: Sodium nitrate is soluble in water (nitrates are generally soluble). Step 3: Write the balanced chemical equation for the reaction Since Ag2CO3 is insoluble, precipitation occurs when Na2CO3 and AgNO3 solutions are mixed. The balanced chemical equation is: \( 2\mathrm{AgNO}_{3}(aq) + \mathrm{Na}_{2}\mathrm{CO}_{3}(aq) \rightarrow \mathrm{Ag}_{2}\mathrm{CO}_{3}(s) + 2\mathrm{NaNO}_{3}(aq) \)

(b) Mixing NaNO3 and NiSO4 solutions

Step 1: Write the possible products' chemical formulas By mixing \(\mathrm{NaNO}_{3}\) and \(\mathrm{NiSO}_{4}\) solutions, we can have the following possible products: Na2SO4 and Ni(NO3)2 Step 2: Determine their solubility according to solubility rules Na2SO4: Sodium sulfate is soluble in water (most sulfates are soluble, and alkali metal compounds are soluble). Ni(NO3)2: Nickel nitrate is soluble in water (nitrates are generally soluble) Step 3: Write the balanced chemical equation for the reaction As both the possible products formed are soluble, there will be no precipitation when NaNO3 and NiSO4 solutions are mixed.

(c) Mixing FeSO4 and Pb(NO3)2 solutions

Step 1: Write the possible products' chemical formulas By mixing \(\mathrm{FeSO}_{4}\) and \(\mathrm{Pb(NO}_{3})_{2}\) solutions, we can have the following possible products: PbSO4 and Fe(NO3)2 Step 2: Determine their solubility according to solubility rules PbSO4: Lead sulfate is generally insoluble in water. Fe(NO3)2: Iron(II) nitrate is soluble in water (nitrates are generally soluble). Step 3: Write the balanced chemical equation for the reaction Since PbSO4 is insoluble, precipitation occurs when FeSO4 and Pb(NO3)2 solutions are mixed. The balanced chemical equation is: \( \mathrm{FeSO}_{4}(aq) + \mathrm{Pb(NO}_{3})_{2}(aq) \rightarrow \mathrm{PbSO}_{4}(s) + \mathrm{Fe(NO}_{3})_{2}(aq) \)

Key concepts

Precipitation Reactions

Precipitation reactions occur when two solutions are mixed, and an insoluble solid, known as a precipitate, is formed. When a chemical reaction takes place, the ions in the solution rearrange themselves to create new compounds. If the new compound formed is insoluble in water, it will appear as a solid precipitate, separating from the solution.
The process is similar to mixing two different solutions of salt and watching as a solid forms at the bottom. This is because the product of the mix is not soluble, meaning it cannot dissolve in the liquid, thus leading to the formation of a solid.

• For example, when solutions of sodium carbonate (\(\text{Na}_2\text{CO}_3\)) and silver nitrate (\(\text{AgNO}_3\)) are combined, a white solid, silver carbonate (\(\text{Ag}_2\text{CO}_3\)), forms as a precipitate.

Identifying when and why these reactions occur is critical in chemistry and requires an understanding of solubility rules, which help predict whether a substance will dissolve or form a precipitate.

Solubility Rules

Solubility rules help chemists predict whether a particular compound will dissolve in water. These guidelines are based on the general behavior of ions in a solution. Solubility rules are essential for predicting the outcomes of precipitation reactions.
Certain ions typically form soluble compounds, while others do not.

• Nitrates (\(\text{NO}_3^-\)) and alkali metal ions, such as sodium (\(\text{Na}^+\)), are generally soluble in water regardless of the counter ion.
• Most sulfates (\(\text{SO}_4^{2-}\)) are soluble, except with barium, lead, and calcium.
• Carbonates (\(\text{CO}_3^{2-}\)) and phosphates (\(\text{PO}_4^{3-}\)) tend to be insoluble unless paired with alkali metals.

By applying these rules, chemists can determine that mixing sodium carbonate and silver nitrate forms an insoluble silver carbonate, leading to precipitation. However, combining sodium nitrate and nickel sulfate results in a soluble solution with no precipitate.

Balanced Chemical Equations

Balanced chemical equations are vital in representing chemical reactions, ensuring that the atoms involved are perfectly accounted for on both sides of the reaction. This principle is based on the conservation of mass—the idea that matter cannot be created or destroyed.
A balanced equation simply means that the number of each type of atom is the same on both the reactant and product sides of the equation.

• For example, when balancing the reaction between sodium carbonate and silver nitrate to form silver carbonate and sodium nitrate:\[2\text{AgNO}_3(aq) + \text{Na}_2\text{CO}_3(aq) \rightarrow \text{Ag}_2\text{CO}_3(s) + 2\text{NaNO}_3(aq)\]Each side is examined to ensure they have the same number of silver (Ag), nitrogen (N), oxygen (O), sodium (Na), and carbon (C) atoms.

Balancing equations is crucial for accurately predicting the amounts of reactants needed and the products formed in a chemical reaction.