Question

Complete and balance each acid-base reaction. (a) \(\mathrm{HCl}(a q)+\mathrm{Ba}(\mathrm{OH})_{2}(a q)\) (b) \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{KOH}(a q)\) (c) \(\mathrm{HClO}_{4}(a q)+\mathrm{NaOH}(a q) \longrightarrow\)

Short answer

The complete and balanced reactions are: (a) \(2\mathrm{HCl} + \mathrm{Ba(OH)}_2 \rightarrow \mathrm{BaCl}_2 + 2\mathrm{H}_2\mathrm{O}\), (b) \(\mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{KOH} \rightarrow \mathrm{K}_2\mathrm{SO}_4 + 2\mathrm{H}_2\mathrm{O}\), (c) \(\mathrm{HClO}_4 + \mathrm{NaOH} \rightarrow \mathrm{NaClO}_4 + \mathrm{H}_2\mathrm{O}\).

Step-by-step solution

- Balance the reaction between HCl and Ba(OH)2

First, write down the products of the reaction. HCl is an acid and Ba(OH)2 is a base. The products of an acid-base reaction are typically water (H2O) and a salt. In this case, the salt will be BaCl2.Now, balance the chemical equation:\[\mathrm{HCl} + \mathrm{Ba(OH)}_2 \rightarrow \mathrm{BaCl}_2 + \mathrm{H}_2\mathrm{O}\]For every molecule of Ba(OH)2, there are 2 OH- groups, so we need 2 HCl molecules to neutralize them and to produce 2 H2O molecules. The balanced reaction is:\[2\mathrm{HCl} + \mathrm{Ba(OH)}_2 \rightarrow \mathrm{BaCl}_2 + 2\mathrm{H}_2\mathrm{O}\]

- Balance the reaction between H2SO4 and KOH

First, write down the expected products. H2SO4 and KOH will form water (H2O) and potassium sulfate (K2SO4) as the salt.Balance the chemical equation:\[\mathrm{H}_2\mathrm{SO}_4 + \mathrm{KOH} \rightarrow \mathrm{K}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O}\]Since H2SO4 has 2 hydrogen ions and KOH has only 1, two KOH molecules will be needed to neutralize one molecule of H2SO4 and produce 2 molecules of water. The balanced reaction is:\[\mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{KOH} \rightarrow \mathrm{K}_2\mathrm{SO}_4 + 2\mathrm{H}_2\mathrm{O}\]

- Balance the reaction between HClO4 and NaOH

As with the previous reactions, the products will be salt and water. For HClO4 and NaOH, the products will be sodium perchlorate (NaClO4) and water (H2O).So the unbalanced reaction looks like this:\[\mathrm{HClO}_4 + \mathrm{NaOH} \rightarrow \mathrm{NaClO}_4 + \mathrm{H}_2\mathrm{O}\]Since there's one OH- in NaOH and one H+ from HClO4, we need only one molecule of each to produce one water molecule. Thus, the balanced reaction is already correctly balanced as written.

Key concepts

Chemical Equation Balancing

Balancing chemical equations is essential because it reflects the law of conservation of mass, indicating that matter cannot be created or destroyed in a chemical reaction. To balance an equation, each element must have the same number of atoms on both the reactant and product sides.

For a balanced reaction to occur, like the neutralization between hydrochloric acid (HCl) and barium hydroxide (Ba(OH)₂), we observe that barium hydroxide has two hydroxide ions. Therefore, two hydrochloric acid molecules are required to produce two water molecules, ensuring that the number of hydrogen and chlorine atoms are equal on both sides of the equation. This results in the balanced equation:
\[2\mathrm{HCl}(aq) + \mathrm{Ba(OH)}_2(aq) \rightarrow \mathrm{BaCl}_2(s) + 2\mathrm{H}_2\mathrm{O}(l)\].

This principle of balancing equations applies to all chemical reactions and is crucial for accurate stoichiometric calculations in chemistry.

Neutralization Reactions

Neutralization reactions are a specific type of chemical reaction where an acid and a base interact to form water and a salt. An acid is a substance that can donate a proton (H⁺), while a base can accept a proton. In a neutralization reaction, the H⁺ from the acid combines with the OH^- from the base to form water (H₂O).

For example, sulfuric acid (H₂SO₄), when reacting with potassium hydroxide (KOH), undergoes a neutralization reaction to produce potassium sulfate (K₂SO₄) and water:
\[\mathrm{H}_2\mathrm{SO}_4(aq) + 2\mathrm{KOH}(aq) \rightarrow \mathrm{K}_2\mathrm{SO}_4(aq) + 2\mathrm{H}_2\mathrm{O}(l)\].

Neutralization reactions are important in various applications, such as titration in analytical chemistry and the treatment of acid reflux in medicine.

Salt Formation in Chemistry

Salt formation is a fundamental outcome of neutralization reactions, where the acid's cation (positively charged ion) and the base's anion (negatively charged ion) combine to form a new compound. Salts are ionic compounds that do not necessarily have to come from sodium chloride (table salt) but can form from various acid and base combinations.

For instance, when perchloric acid (HClO₄) meets sodium hydroxide (NaOH), sodium perchlorate (NaClO₄) is the resulting salt, along with water, in the balanced equation:
\[\mathrm{HClO}_4(aq) + \mathrm{NaOH}(aq) \rightarrow \mathrm{NaClO}_4(aq) + \mathrm{H}_2\mathrm{O}(l)\].

Salts are essential for various applications in daily life and industries, such as food preservation, fertilizers, and even in pharmacology where certain salts are used to improve medicine solubility.

Stoichiometry

Stoichiometry is the mathematical relationship between the quantities of reactants and products in a chemical reaction. It's based on the balanced equations, which provides a ratio of how much of each compound is needed or formed.

For example, the stoichiometry of the reaction between hydrochloric acid and barium hydroxide discussed previously shows us that two moles of hydrochloric acid react with one mole of barium hydroxide to produce one mole of barium chloride and two moles of water. Such stoichiometric ratios are crucial for predicting the amount of products formed and for preparing reactions so that all reactants are consumed, which is especially significant in industrial settings for maximizing efficiency and reducing waste.