Question

Complete the following acid-base reactions by indicating the acid and base that must have reacted in each case to produce the indicated salt. a. \(+\rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)\) b. \(+\rightarrow \mathrm{NaNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\) c. \(+\rightarrow \mathrm{CaCl}_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)\) d. \(+\rightarrow \mathrm{Ba}\left(\mathrm{ClO}_{4}\right)_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)\)

Short answer

a. 2KOH(aq) + H_2SO_4(aq) \rightarrow K_2SO_4(aq) + 2H_2O(l) b. NaOH(aq) + HNO_3(aq) \rightarrow NaNO_3(aq) + H_2O(l) c. Ca(OH)_2(aq) + 2HCl(aq) \rightarrow CaCl_2(aq) + 2H_2O(l) d. Ba(OH)_2(aq) + 2HClO_4(aq) \rightarrow Ba(ClO_4)_2(aq) + 2H_2O(l)

Step-by-step solution

a. Determine the acid and base for the reaction #a. Determine the acid and base for the reactionproducing \(K_2SO_4(aq) + 2H_2O(l)\)

: The salt produced is \(K_2SO_4(aq)\), which is made up of potassium (K) and sulfate (SO_4) ions. The potassium ion (K) comes from a base, while the sulfate (SO_4) ion comes from an acid. The base that contains potassium (K) is potassium hydroxide (KOH), and the acid that contains sulfate (SO_4) is sulfuric acid (H_2SO_4). Therefore, the reaction is: \[2KOH(aq) + H_2SO_4(aq) \rightarrow K_2SO_4(aq) + 2H_2O(l)\]

b. Determine the acid and base for the reaction producing \(NaNO_3(aq) + H_2O(l)\)

: The salt produced is \(NaNO_3(aq)\), which is made up of sodium (Na) and nitrate (NO_3) ions. The sodium ion (Na) comes from a base, while the nitrate (NO_3) ion comes from an acid. The base that contains sodium (Na) is sodium hydroxide (NaOH), and the acid that contains nitrate (NO_3) is nitric acid (HNO_3). Therefore, the reaction is: \[NaOH(aq) + HNO_3(aq) \rightarrow NaNO_3(aq) + H_2O(l)\]

c. Determine the acid and base for the reaction producing \(CaCl_2(aq) + 2H_2O(l)\)

: The salt produced is \(CaCl_2(aq)\), which is made up of calcium (Ca) and chloride (Cl) ions. The calcium ion (Ca) comes from a base, while the chloride (Cl) ion comes from an acid. The base that contains calcium (Ca) is calcium hydroxide (Ca(OH)_2), and the acid that contains chloride (Cl) is hydrochloric acid (HCl). Therefore, the reaction is: \[Ca(OH)_2(aq) + 2HCl(aq) \rightarrow CaCl_2(aq) + 2H_2O(l)\]

d. Determine the acid and base for the reaction producing \(Ba(ClO_4)_2(aq) + 2H_2O(l)\)

: The salt produced is \(Ba(ClO_4)_2(aq)\), which is made up of barium (Ba) and perchlorate (ClO_4) ions. The barium ion (Ba) comes from a base, while the perchlorate (ClO_4) ion comes from an acid. The base that contains barium (Ba) is barium hydroxide (Ba(OH)_2), and the acid that contains perchlorate (ClO_4) is perchloric acid (HClO_4). Therefore, the reaction is: \[Ba(OH)_2(aq) + 2HClO_4(aq) \rightarrow Ba(ClO_4)_2(aq) + 2H_2O(l)\]

Key concepts

Neutralization Reaction

A neutralization reaction is a fundamental chemical reaction where an acid and a base react to form water and a salt. It is one of the most straightforward examples of an acid-base reaction and is described by the general equation:
\[\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}\]
The heart of this process is the transfer of a proton (H⁺) from the acid to the base. This proton transfer neutralizes both the acid and base, leading to the creation of water (H₂O) and an ionic compound known as salt. For instance, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the result is water and sodium chloride (NaCl), a common table salt:
\[HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)\]
When writing neutralization reactions, it's essential to identify the acid and base involved in the reaction. This often requires understanding the ions that make up common acids and bases and how they combine to form salts during the reaction. Regular practice with different pairs of acids and bases can sharpen this skill, helping you to quickly identify the reactants and predict the products of these reactions.

Salt Formation

In the context of chemistry, salt formation refers to the creation of an ionic compound when an acid reacts with a base. Salts are composed of positively charged ions (cations), usually from the base, and negatively charged ions (anions), typically from the acid. A salt's characteristics, including its solubility, melting point, and crystalline structure, depend on the nature of these ions.
During a neutralization reaction, salts are formed alongside water. For example, in the reaction to form potassium sulfate (\(K_2SO_4\)), potassium ions (\(K^+\)) from potassium hydroxide (KOH) combine with sulfate ions (\(SO_4^{2-}\)) from sulfuric acid (\(H_2SO_4\)):
\[2KOH(aq) + H_2SO_4(aq) \rightarrow K_2SO_4(aq) + 2H_2O(l)\]
Recognizing the acid and base that cause salt formation is crucial, not only in predicting the products of a reaction but also in applications such as neutralizing soil pH or formulating pharmaceuticals. The abilities to predict salt solubility and understand their role in different chemical environments are essential skills in chemistry.

Chemical Equations

Chemical equations are symbolic representations of chemical reactions, showing the reactants and products along with their respective quantities. Writing balanced chemical equations is vital for understanding the law of conservation of mass, which states that matter is neither created nor destroyed in a chemical reaction. A correctly balanced chemical equation ensures that the number of atoms of each element is the same on both sides of the equation.
For instance, the neutralization reaction between calcium hydroxide (\(Ca(OH)_2\)) and hydrochloric acid (\(HCl\)) to form calcium chloride (\(CaCl_2\)) and water is represented by the equation:
\[Ca(OH)_2(aq) + 2HCl(aq) \rightarrow CaCl_2(aq) + 2H_2O(l)\]

Balancing Chemical Equations

Begin by listing all the elements involved in the reaction and compare the number of atoms of each on both reaction and product sides. Adjust coefficients—never subscripts of compounds—to balance the atoms. Practice is key to mastering the balancing of chemical equations. Use the coefficients to also understand the molar ratios in reactions, which can help when calculating reactants or products in stoichiometry problems.