Question

Write a balanced net ionic equation for each of the following acid-base reactions in water. (a) acetic acid \(\left(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)\) with strontium hydroxide (b) diethylamine, \(\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}\), with sulfuric acid (c) aqueous hydrogen cyanide (HCN) with sodium hydroxide

Short answer

Question: Write the balanced net ionic equations for the following reactions: (a) Acetic acid (HC2H3O2) with strontium hydroxide (b) Diethylamine (C2H5)2NH with sulfuric acid (c) Aqueous hydrogen cyanide (HCN) with sodium hydroxide Answer: (a) HC2H3O2 (aq) + 2 OH- (aq) -> 2 CH3COO- (aq) + 2 H2O (l) (b) (C2H5)2NH (aq) + H2SO4 (aq) -> (C2H5)2NH2+ (aq) + HSO4- (aq) (c) HCN (aq) + OH- (aq) -> CN- (aq) + H2O (l)

Step-by-step solution

Write the balanced complete ionic equation

For the reaction between acetic acid and strontium hydroxide, first write the reactants and products. Acetic acid is a weak acid that will donate a proton to the hydroxide ion from the strong base strontium hydroxide, forming aqueous acetate ions and water. The complete balanced equation is: HC2H3O2 (aq) + Sr(OH)2 (aq) -> 2 CH3COO- (aq) + Sr2+ (aq) + 2 H2O (l)

Identify and remove spectator ions

The spectator ion in this reaction is the strontium cation, Sr2+. So, we remove this ion from both sides of the equation.

Write the balanced net ionic equation

After removing the spectator ion, the net ionic equation is: HC2H3O2 (aq) + 2 OH- (aq) -> 2 CH3COO- (aq) + 2 H2O (l) (b) Diethylamine (C2H5)2NH with sulfuric acid

Write the balanced complete ionic equation

Diethylamine, a weak base, will accept a proton from the strong acid sulfuric acid. This will form aqueous diethylammonium ions and hydrogen sulfate ions. The complete balanced equation is: (C2H5)2NH (aq) + H2SO4 (aq) -> (C2H5)2NH2+ (aq) + HSO4- (aq)

Identify and remove spectator ions

There are no spectator ions in this reaction since all components are involved in the reaction.

Write the balanced net ionic equation

The net ionic equation is the same as the complete ionic equation in this case: (C2H5)2NH (aq) + H2SO4 (aq) -> (C2H5)2NH2+ (aq) + HSO4- (aq) (c) Aqueous hydrogen cyanide (HCN) with sodium hydroxide

Write the balanced complete ionic equation

Aqueous hydrogen cyanide, a weak acid, will donate a proton to the hydroxide ion from the strong base sodium hydroxide, forming water and aqueous cyanide ions. The complete balanced equation is: HCN (aq) + NaOH (aq) -> NaCN (aq) + H2O (l)

Identify and remove spectator ions

The spectator ion in this reaction is the sodium cation, Na+. So, we remove this ion from both sides of the equation.

Write the balanced net ionic equation

After removing the spectator ion, the net ionic equation is: HCN (aq) + OH- (aq) -> CN- (aq) + H2O (l)

Key concepts

Acid-Base Reactions

Acid-base reactions are fascinating chemical reactions where an acid reacts with a base to produce salt and water. This process is often referred to as neutralization. In these reactions, the acid donates a proton (H⁺) to the base.

Here's a deeper look into what happens:

• **Acids** are substances that can donate a proton or hydrogen ion. Depending on their strength, which relates to how easily they donate protons, they are categorized as strong or weak acids.
• **Bases** are substances that can accept a proton. Like acids, they can also be strong or weak, based on their ability to accept protons.

Acid-base reactions are fundamental in many chemical and biological processes, including digestion in our stomachs, which involves hydrochloric acid. In this exercise, acetic acid (a weak acid) and strontium hydroxide (a strong base) react. Through this reaction, hydrogen ions from acetic acid combine with hydroxide ions from strontium hydroxide to form water.

Chemical Equations

Chemical equations are symbolic representations of chemical reactions. They show the reactants on the left and the products on the right, connected by an arrow.

This compact way of using symbols and formulas informs us about:

• **Reactants and Products:** The substances that start the reaction and those produced by the reaction.
• **Physical State:** Represented by letters in parentheses beside each chemical, such as (aq) for aqueous solutions, indicating the substance is dissolved in water.
• **Reaction Conditions:** Sometimes, equations include conditions such as temperature or catalysts needed for the reaction to proceed.

Writing out a chemical equation involves identifying each participant in the reaction and ensuring all components account for. This exercise involves writing chemical equations for various acid-base reactions, a crucial skill for understanding how different chemicals interact.

Spectator Ions

Spectator ions are ions that appear on both the reactant and product sides of a balanced equation. While they are part of the ionic compounds involved, they do not participate in the actual acid-base reaction. Their presence is only noted to balance the charge of the equation. When writing net ionic equations, these ions are removed to focus on the actual substances participating in the reaction.

In most acid-base reactions, especially those involving strong electrolytes, spectator ions are present. For example, when acetic acid reacts with strontium hydroxide, the strontium ions, which don't participate in the reaction, are eliminated from the net ionic equation. This step simplifies the process and highlights the essential acid-base neutralization.

Balancing Equations

Balancing equations is a key concept in chemistry to ensure mass and charge are conserved during a reaction. This means that the number of atoms for each element and the overall charge must be the same on both sides of the equation.

Here's how you can approach balancing chemical equations:

• **Identify the Elements:** Check the type and number of atoms on both sides of the equation.
• **Balance One Element at a Time:** Start with elements that appear in only one reactant and product to make it simpler. Adjust coefficients as needed.
• **Balance Complex Ions as Units:** If a polyatomic ion doesn’t change during the reaction, balance it as a single unit.
• **Check Your Work:** Ensure both sides have the same number of atoms for each element and the charges are balanced.

In this exercise, after writing ionic equations for acid-base reactions, balancing ensures that all atoms and charges are accounted for, leading to a meaningful chemical equation.