Question

Write balanced complete ionic and net ionic equations for each acid-base reaction. a. \(\mathrm{HBr}(a q)+\mathrm{NaOH}(a q)\) b. \(\mathrm{HF}(a q)+\mathrm{NaOH}(a q) \longrightarrow\) c. \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)+\mathrm{RbOH}(a q) \longrightarrow\)

Short answer

Complete ionic and net ionic equations for the given reactions:ea) Net ionic: H+(aq) + OH-(aq) → H2O(l).b) Net ionic: HF(aq) + OH-(aq) → F-(aq) + H2O(l).c) Net ionic: HC2H3O2(aq) + OH-(aq) → C2H3O2-(aq) + H2O(l).

Step-by-step solution

Write the balanced molecular equations

First, write down the balanced molecular equations for each reaction. ea) HBr(aq) + NaOH(aq) → NaBr(aq) + H2O(l).b) HF(aq) + NaOH(aq) → NaF(aq) + H2O(l).c) HC2H3O2(aq) + RbOH(aq) → RbC2H3O2(aq) + H2O(l).

Write the complete ionic equations

Next, write out the complete ionic equations by breaking all soluble ionic compounds into their constituent ions.ea) H+(aq) + Br-(aq) + Na+(aq) + OH-(aq) → Na+(aq) + Br-(aq) + H2O(l).b) HF(aq) does not dissociate completely as it is a weak acid + Na+(aq) + OH-(aq) → Na+(aq) + F-(aq) + H2O(l).c) HC2H3O2(aq) is a weak acid and does not dissociate completely + Rb+(aq) + OH-(aq) → Rb+(aq) + C2H3O2- (aq) + H2O(l).

Cancel the spectator ions

Cancel out the ions that appear on both sides of the equation to find the net ionic equations.ea) H+(aq) + OH-(aq) → H2O(l).b) HF(aq) + OH-(aq) → F-(aq) + H2O(l).c) HC2H3O2(aq) + OH-(aq) → C2H3O2- (aq) + H2O(l).

Key concepts

Acid-Base Reaction

An acid-base reaction is a chemical process where an acid and a base interact to form water and a salt. Typically, in aqueous solutions, acids donate protons (H+) to the bases. The strength of an acid (or base) is crucial in determining the extent of the reaction. For example, in the reaction of hydrobromic acid (HBr) with sodium hydroxide (NaOH), the strong acid HBr donates a proton to the strong base OH-, forming water (H2O) and sodium bromide (NaBr), a salt.

Identifying the type of acids and bases involved influences how we approach the reaction. In our exercise, for instance, hydrofluoric acid (HF) and acetic acid (HC2H3O2) are weak acids, which means they do not completely dissociate in water, affecting the ions present in the complete ionic equation and consequently the net ionic equation.

Complete Ionic Equations

Complete ionic equations provide a more detailed perspective than the overall balanced chemical equations. They represent all strong electrolytes as ions that they form in an aqueous solution. For example, the reaction between HBr and NaOH in aqueous solution, when represented as a complete ionic equation, shows all the ions: H+, Br-, Na+, and OH- separately.

Understanding Complete Ionic Equations

These equations show us exactly which ions are present in the solution before they react, and what products are formed after the reaction. However, weak electrolytes like HF and HC2H3O2 (weak acids in our examples), are not fully represented as ions because they don't fully ionize in solution. It’s important for students to recognize and accurately represent strong and weak electrolytes when writing complete ionic equations.

Spectator Ions

Spectator ions are ions that do not partake in the actual chemical reaction and can be found unchanged on both the reactant and product sides of a complete ionic equation. They are called 'spectator' ions because they are essentially watching the reaction happen without participating. In our exercise examples, Na+ and Br- in the first reaction and Rb+ in the third reaction are spectator ions.

Role of Spectator Ions

The presence of spectator ions is important as they provide ionic strength and conductivity to the solution, but they do not influence the outcome of the reaction. When writing net ionic equations, we omit these spectator ions, which simplifies the equation to show only the species that actually participate in the reaction.

Weak Acids

Weak acids, such as hydrofluoric acid (HF) and acetic acid (HC2H3O2), only partially dissociate into ions in aqueous solutions. This partial dissociation makes the complete ionic equation different from strong acids, which fully dissociate.

Behavior of Weak Acids in Reactions

Since weak acids do not completely release their hydrogen ions, the reaction with a base will have a different ionic makeup compared to a reaction involving a strong acid. This characteristic also modifies the net ionic equation. In the reactions from our exercise, HF and HC2H3O2 are not broken down into their constituent ions completely, reflecting their nature as weak acids and affecting the balance and form of the complete and net ionic equations.

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is respected in a chemical reaction. Each element must have the same number of atoms on both the reactant and product sides of the equation. This process is not just a rote skill but also an expression of the stoichiometric relationships between reactants and products.

Steps to Balancing Equations

To balance equations, you count the number of atoms of each element in the reactants and products and add coefficients to the compounds to even them out. For example, HBr reacting with NaOH to produce NaBr and H2O is already balanced. In contrast, more complex reactions like the third exercise involving acetic acid (HC2H3O2) require careful stoichiometric balancing to ensure the correct representation of the substances before and after the reaction.