Question

Complete and balance each acid-base reaction. (a) \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)+\mathrm{Ca}(\mathrm{OH})_{2}(a q) \longrightarrow\) (b) \(\operatorname{HBr}(a q)+\operatorname{LiOH}(a q) \longrightarrow\) (c) \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q)\)

Short answer

(a) \(2\mathrm{HC}_2\mathrm{H}_3\mathrm{O}_2(aq) + \mathrm{Ca}(\mathrm{OH})_2(aq) \longrightarrow \mathrm{Ca(C}_2\mathrm{H}_3\mathrm{O}_2)_2(aq) + 2\mathrm{H}_2\mathrm{O}(l)\), (b) \(\mathrm{HBr}(aq) + \mathrm{LiOH}(aq) \longrightarrow \mathrm{LiBr}(aq) + \mathrm{H}_2\mathrm{O}(l)\), (c) \(\mathrm{H}_2\mathrm{SO}_4(aq) + \mathrm{Ba}(\mathrm{OH})_2(aq) \longrightarrow \mathrm{BaSO}_4(s) + 2\mathrm{H}_2\mathrm{O}(l)\).

Step-by-step solution

Identify the Acid and Base

In each reaction, identify the acid (donates protons) and the base (accepts protons). For (a), \(\mathrm{HC}_2\mathrm{H}_3\mathrm{O}_2\) is the acid and \(\mathrm{Ca}(\mathrm{OH})_2\) is the base. In (b), \(\mathrm{HBr}\) is the acid and \(\mathrm{LiOH}\) is the base. Finally, in (c), \(\mathrm{H}_2\mathrm{SO}_4\) is the acid and \(\mathrm{Ba}(\mathrm{OH})_2\) is the base.

Write the Products

Acid-base reactions typically form water (H2O) and a salt. The product of (a) will be acetic salt (\(\mathrm{Ca(C}_2\mathrm{H}_3\mathrm{O}_2)_2\)) and water (H2O). Similarly, for (b), the products will be lithium bromide (LiBr) and water (H2O), and for (c), the products will be barium sulfate (\(\mathrm{BaSO}_4\)) and water (H2O).

Balance the Reaction

Make sure the number of atoms of each element is equal on both sides of the equation. For (a), the balanced reaction is \(2\mathrm{HC}_2\mathrm{H}_3\mathrm{O}_2(aq) + \mathrm{Ca}(\mathrm{OH})_2(aq) \longrightarrow \mathrm{Ca(C}_2\mathrm{H}_3\mathrm{O}_2)_2(aq) + 2\mathrm{H}_2\mathrm{O}(l)\). For (b), the balanced reaction is \(\mathrm{HBr}(aq) + \mathrm{LiOH}(aq) \longrightarrow \mathrm{LiBr}(aq) + \mathrm{H}_2\mathrm{O}(l)\). Finally, for (c), the balanced reaction is \(\mathrm{H}_2\mathrm{SO}_4(aq) + \mathrm{Ba}(\mathrm{OH})_2(aq) \longrightarrow \mathrm{BaSO}_4(s) + 2\mathrm{H}_2\mathrm{O}(l)\).

Key concepts

Acid and Base Identification

Recognizing acids and bases is crucial in chemistry, especially in acid-base reactions. By definition, an acid is a substance that can donate a proton (hydrogen ion, H⁺), and a base is a substance that can accept a proton. The process of identifying an acid or base in a reaction involves looking for compounds that typically possess certain characteristics.

• Acids commonly start with hydrogen (e.g., HCl, H₂SO₄), have a sour taste, can turn blue litmus paper red, and react with metals to produce hydrogen gas.
• Bases often contain a hydroxide ion (OH^-), have a bitter taste, a slippery feel, and can turn red litmus paper blue.

In our textbook examples, the acids are HC₂H₃O₂, HBr, and H₂SO₄, which are substances starting with hydrogen and ready to donate protons. The bases are Ca(OH)₂, LiOH, and Ba(OH)₂, all of which contain the hydroxide ion, making them capable of accepting protons.

Chemical Reaction Balancing

Balancing chemical reactions is a fundamental skill in chemistry that ensures the law of conservation of mass is obeyed. For a reaction to be balanced, each element must have the same number of atoms on both the reactant and product sides. This is achieved through manipulating coefficients—the numbers placed in front of compounds—in the reaction.

• First, list all the elements present in the reaction.
• Determine the number of atoms for each element on both sides of the equation.
• Adjust coefficients to obtain the same number of atoms of each element on both sides.
• Double-check your work to ensure all atoms balance and that the coefficients are the smallest set of whole numbers possible.

Let's look at the provided reaction (a) as an example. We start with 2 molecules of acetic acid (HC₂H₃O₂) and 1 molecule of calcium hydroxide (Ca(OH)₂). By placing the coefficient '2' in front of HC₂H₃O₂, we balance the hydrogen and oxygen atoms forming 2 water molecules (H₂O) and a molecule of calcium acetate Ca(C₂H₃O₂)₂.

Acid-Base Neutralization

Acid-base neutralization reactions are specific types of chemical reactions where an acid reacts with a base to produce water and a salt. This process is important both in natural processes and industrial applications. The acid's protons (H⁺) react with the base's hydroxide ions (OH^-) to form water (H₂O). The remaining ions from the acid and base combine to form a salt.

General Form of an Acid-Base Reaction

An acid-base neutralization can be generally represented as:

Acid (H⁺ donor) + Base (OH^- acceptor) → Water (H₂O) + Salt

• In example (b), hydrobromic acid (HBr) neutralizes lithium hydroxide (LiOH) to form lithium bromide (LiBr) and water.
• Similarly, in example (c), sulfuric acid (H₂SO₄) reacts with barium hydroxide (Ba(OH)₂) to create barium sulfate (BaSO₄) and water.

Understanding neutralization reactions helps in various applications, including titrations in laboratory settings, stomach antacid formulations, and the treatment of acid spills.