Question

For each acid-base pair, write a balanced equation for the neutralization reaction: (a) Lithium hydroxide and hydroiodic acid (b) Acetic acid and sodium hydroxide (c) Hydrobromic acid and calcium hydroxide (d) Potassium hydroxide and phosphoric acid (assume all acidic protons react)

Short answer

(a) \(LiOH + HI \rightarrow H_2O + LiI\) (b) \(CH_3COOH + NaOH \rightarrow H_2O + CH_3COONa\) (c) \(2HBr + Ca(OH)_2 \rightarrow 2H_2O + CaBr_2\) (d) \(3KOH + H_3PO_4 \rightarrow 3H_2O + K_3PO_4\)

Step-by-step solution

(a) Write the reaction for Lithium hydroxide and Hydroiodic acid

First, we need to identify the formulas for each compound involved: Lithium hydroxide: \(LiOH\) Hydroiodic acid: \(HI\) Now write the equation: \(LiOH + HI \rightarrow \) In a neutralization reaction, the products are water and a salt. The salt consists of the cation from the base and the anion from the acid. Here the salt is lithium iodide (\(LiI\)) Final balanced equation: \(LiOH + HI \rightarrow H_2O + LiI\)

(b) Write the reaction for Acetic acid and Sodium hydroxide

Identify the formulas for each compound involved: Acetic acid: \(CH_3COOH\) Sodium hydroxide: \(NaOH\) Now write the equation: \(CH_3COOH + NaOH \rightarrow \) The products are water and a salt. The salt is sodium acetate (\(CH_3COONa\)) Final balanced equation: \(CH_3COOH + NaOH \rightarrow H_2O + CH_3COONa\)

(c) Write the reaction for Hydrobromic acid and Calcium hydroxide

Identify the formulas for each compound involved: Hydrobromic acid: \(HBr\) Calcium hydroxide: \(Ca(OH)_2\) Now write the equation: \(HBr + Ca(OH)_2 \rightarrow \) The products are water and a salt. The salt is calcium bromide (\(CaBr_2\)) To balance the equation, we need 2 moles of Hydrobromic acid for each mole of Calcium hydroxide: Final balanced equation: \(2HBr + Ca(OH)_2 \rightarrow 2H_2O + CaBr_2\)

(d) Write the reaction for Potassium hydroxide and Phosphoric acid

Identify the formulas for each compound involved: Potassium hydroxide: \(KOH\) Phosphoric acid: \(H_3PO_4\) Now write the equation: \(KOH + H_3PO_4 \rightarrow \) The products are water and a salt. The salt is potassium phosphate (\(K_3PO_4\)) Since all acidic protons react, we need 3 moles of Potassium hydroxide for each mole of Phosphoric acid to balance the equation: Final balanced equation: \(3KOH + H_3PO_4 \rightarrow 3H_2O + K_3PO_4\)

Key concepts

Understanding Acid-Base Pairs

Acid-base pairs are key players in chemistry, especially when it comes to reactions like neutralization, where an acid and a base react to form water and a salt. An acid is a substance that can donate a proton (H+), while a base is a substance that can accept a proton. When combined in a reaction, they form conjugate acid-base pairs.

For example, in the neutralization reaction between lithium hydroxide (LiOH), a base, and hydroiodic acid (HI), an acid, lithium iodide (LiI) and water (H₂O) are formed. Here, HI donates a proton to LiOH, and the Li+ cation from the base pairs with the I- anion from the acid to form LiI, the salt. This demonstrates how acid-base pairs interact in a neutralization reaction, perfectly illustrating the hand-in-glove compatibility of acids and bases that result in such products.

Writing Balanced Chemical Equations

Writing balanced chemical equations is essential for understanding chemical reactions. The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction, meaning all atoms in the reactants must be accounted for in the products.

To write a balanced equation, one must first write the skeleton equation with the correct formulas for all reactants and products, as was done in the exercise for acetic acid (CH₃COOH) and sodium hydroxide (NaOH). After this, coefficients are adjusted to ensure the same number of each type of atom appears on both sides of the equation. In the neutralization of hydrobromic acid (HBr) and calcium hydroxide (Ca(OH)₂), the equation is balanced by having two HBr molecules react with one Ca(OH)₂ molecule to produce two water molecules and one calcium bromide (CaBr₂) molecule. It's like solving a puzzle, ensuring that all pieces fit perfectly to preserve the mass of the atoms from reactants to products.

Formation of Salt and Water

The formation of salt and water during a neutralization reaction is a hallmark of acid-base chemistry. Salts are ionic compounds composed of cations from the base and anions from the acid. Water, on the other hand, is a neutral molecule resulting from the combination of H+ ions from the acid and OH- ions from the base.

Consider the reaction of potassium hydroxide (KOH) with phosphoric acid (H₃PO₄). Every KOH molecule contributes a K+ cation, which pairs with the PO₄^3- anion from the phosphoric acid to form potassium phosphate (K₃PO₄). Meanwhile, the OH- from KOH joins with H+ from H₃PO₄ to produce water. Hence, a neutralization reaction is akin to a dance between acids and bases, ending in the formation of salt and the serenity of water.