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) Precipitation occurs between \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (aq) and \(\mathrm{AgNO}_{3}\) (aq). The balanced chemical equation is: \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (aq) + 2 \(\mathrm{AgNO}_{3}\) (aq) \(\rightarrow\) 2 \(\mathrm{NaNO}_{3}\) (aq) + \(\mathrm{Ag}_{2}\mathrm{CO}_{3}\) (s). (b) No precipitation occurs between \(\mathrm{NaNO}_{3}\) (aq) and \(\mathrm{NiSO}_{4}\) (aq). (c) Precipitation occurs between \(\mathrm{FeSO}_{4}\) (aq) and \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) (aq). The balanced chemical equation is: \(\mathrm{FeSO}_{4}\) (aq) + \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) (aq) \(\rightarrow\) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) (aq) + \(\mathrm{PbSO}_{4}\) (s).

Step-by-step solution

(a) Reaction between \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and \(\mathrm{AgNO}_{3}\)

First, let's write down the reactants: \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (aq) + \(\mathrm{AgNO}_{3}\) (aq) Using double displacement, we can predict the possible products: \(\mathrm{NaNO}_{3}\), which is the sodium ion combining with the nitrate ion, and \(\mathrm{Ag}_{2}\mathrm{CO}_{3}\), which is the silver ion combining with the carbonate ion. Now, we need to check if any of the products will precipitate. According to solubility rules, nitrates are soluble, and most carbonates are insoluble. Therefore, the silver carbonate will precipitate, while sodium nitrate will remain soluble. The balanced chemical equation for this reaction is: \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (aq) + 2 \(\mathrm{AgNO}_{3}\) (aq) \(\rightarrow\) 2 \(\mathrm{NaNO}_{3}\) (aq) + \(\mathrm{Ag}_{2}\mathrm{CO}_{3}\) (s)

(b) Reaction between \(\mathrm{NaNO}_{3}\) and \(\mathrm{NiSO}_{4}\)

First, let's write down the reactants: \(\mathrm{NaNO}_{3}\) (aq) + \(\mathrm{NiSO}_{4}\) (aq) Using double displacement, we can predict the possible products: \(\mathrm{Na}_{2}\mathrm{SO}_{4}\), which is the sodium ion combining with the sulfate ion, and \(\mathrm{Ni}\mathrm{NO}_{3}\mathrm{O}\), which is the nickel ion combining with the nitrate ion. Now, we need to check if any of the products will precipitate. According to solubility rules, nitrates and sulfates are soluble. Therefore, there is no precipitation in this reaction.

(c) Reaction between \(\mathrm{FeSO}_{4}\) and \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\)

First, let’s write down the reactants: \(\mathrm{FeSO}_{4}\) (aq) + \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) (aq) Using double displacement, we can predict the possible products: \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\), which is the iron ion combining with the nitrate ion; and \(\mathrm{PbSO}_{4}\), which is the lead ion combining with the sulfate ion. Now, we need to check if any of the products will precipitate. According to solubility rules, nitrates are soluble, while most sulfates are soluble, with a few exceptions including lead sulfate. Therefore, lead sulfate will precipitate in this reaction. The balanced chemical equation for this reaction is: \(\mathrm{FeSO}_{4}\) (aq) + \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) (aq) \(\rightarrow\) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) (aq) + \(\mathrm{PbSO}_{4}\) (s)

Key concepts

Solubility Rules

Understanding solubility rules is essential when predicting whether a precipitation reaction will occur. These rules determine whether a salt (an ionic compound) will dissolve in water. They guide us on which combinations of ions will result in insoluble compounds, leading to the formation of a precipitate. Here are some fundamental solubility rules:

• Most nitrate ( itrate) salts are highly soluble in water.
• Alkali metal salts, such as those containing sodium ( a), potassium ( k), and ammonium ( ) ions, are generally soluble.
• Most chloride ( Cl^- ), bromide ( Br^- ), and iodide ( I^- ) salts are soluble, except those combined with lead ( Pb^{2+} ), silver ( Ag^+ ), and mercury ( Hg_2^{2+} ).
• Most sulfate ( SO_4^{2-} ) salts are soluble, with exceptions for barium ( Ba^{2+} ), calcium ( Ca^{2+} ), and lead ( Pb^{2+} ).
• Carbonates ( CO_3^{2-} ), phosphates ( PO_4^{3-} ), and hydroxides ( OH^- ) are usually insoluble, except when paired with alkali metals.

By utilizing these rules, chemists determine the likelihood of a compound being soluble and predict the formation of a solid precipitate in a reaction.

Double Displacement Reactions

A double displacement reaction, also known as a double replacement or metathesis reaction, occurs when parts of two ionic compounds are exchanged to form two new compounds. This kind of reaction is typically represented as: AB + CD → AD + CB

In this notation, A and B are cations and anions from one compound, while C and D are from another. The ions swap places, forming two new compounds AD and CB.

Key features of double displacement reactions include:

• They often occur in aqueous solutions where ionic compounds are dissolved in water.
• One of the resulting products is usually a precipitate, a gas, or a weakly ionized substance like water, making it easy to separate from the mixture.

To verify if a double displacement reaction will occur, you can check if any of the products are insoluble in water using solubility rules. If one or more products form a solid precipitate, the reaction is successful.

Chemical Equations

Chemical equations are symbolic representations of chemical reactions. They provide concise details about the substances involved, their quantities, and the transformations they undergo. A chemical equation typically looks like this:Reactants → Products

The left side lists the starting chemicals, called reactants, and the right side lists the new substances formed, called products.

Characteristics of balanced chemical equations include:

• The number of atoms for each element is balanced on both sides of the equation, conforming to the law of conservation of mass.
• States of matter for each compound can be denoted using (s) for solids, (l) for liquids, (g) for gases, and (aq) for aqueous solutions.
• Coefficients are used to multiply the number of molecules or atoms, ensuring both sides have equal quantities for each element.

For instance, the equation for the precipitation of lead sulfate is balanced as follows:\[\mathrm{FeSO}_4 \,(aq) + \mathrm{Pb(NO}_3)_2 \,(aq) \rightarrow \mathrm{Fe(NO}_3)_2 \,(aq) + \mathrm{PbSO}_4 \,(s)\]This indicates that one formula unit of iron(II) sulfate and one of lead(II) nitrate yield one formula unit of iron(II) nitrate and one of lead(II) sulfate as a precipitate.