Problem 90 - Chemistry Matter and Change

Question

Give the name and formula of the acid and the base from which each salt was formed. \(\begin{array}{llll}{\text { a. NaCl }} & {\text { b. } \mathrm{KHCO}_{3}} & {\text { c. } \mathrm{NH}_{4} \mathrm{NO}_{2}} & {\text { d. Cas }}\end{array}\)

Step-by-Step Solution

Answer

a. NaCl: Acid: Hydrochloric acid (HCl) Base: Sodium hydroxide (NaOH) b. KHCO3: Acid: Carbonic acid (H2CO3) Base: Potassium hydroxide (KOH) c. NH4NO2: Acid: Ammonium hydroxide (NH4OH) Base: Nitrous acid (HNO2) d. CaS: Acid: Hydrogen sulfide (H2S) Base: Calcium hydroxide (Ca(OH)2)

Step 1: a. Identify the acid and base for NaCl

To identify the acid and base for NaCl, we first look at the constituent ions: Na+ and Cl-. The corresponding acid and base that form NaCl are: 1. Acid: The anion Cl- comes from the acid HCl (hydrochloric acid). Formula: HCl Name: Hydrochloric acid 2. Base: The cation Na+ comes from the base NaOH (sodium hydroxide). Formula: NaOH Name: Sodium hydroxide

Step 2: b. Identify the acid and base for KHCO3

To identify the acid and base for KHCO3, we first look at the constituent ions: K+ and HCO3-. The corresponding acid and base that form KHCO3 are: 1. Acid: The anion HCO3- comes from the acid H2CO3 (carbonic acid). Formula: H2CO3 Name: Carbonic acid 2. Base: The cation K+ comes from the base KOH (potassium hydroxide). Formula: KOH Name: Potassium hydroxide

Step 3: c. Identify the acid and base for NH4NO2

To identify the acid and base for NH4NO2, we first look at the constituent ions: NH4+ and NO2-. The corresponding acid and base that form NH4NO2 are: 1. Acid: The cation NH4+ comes from the acid NH4OH (ammonium hydroxide). Formula: NH4OH Name: Ammonium hydroxide 2. Base: The anion NO2- comes from the acid HNO2 (nitrous acid). Formula: HNO2 Name: Nitrous acid

Step 4: d. Identify the acid and base for CaS

To identify the acid and base for CaS, we first look at the constituent ions: Ca2+ and S2-. The corresponding acid and base that form CaS are: 1. Acid: The anion S2- comes from the acid H2S (hydrogen sulfide). Formula: H2S Name: Hydrogen sulfide 2. Base: The cation Ca2+ comes from the base Ca(OH)2 (calcium hydroxide). Formula: Ca(OH)2 Name: Calcium hydroxide

Key Concepts

Acid and Base Identification

The process of identifying acids and bases is crucial in understanding chemical reactions, particularly those involving salts. Each salt is formed through the combination of an acid and a base, and recognizing these can help clarify reactions and properties of the resulting compounds.

To identify acids and bases in salts:

• Look at the ion composition of the salt.
• The cation (positive ion) usually originates from the base, while the anion (negative ion) comes from the acid.

For example, in NaCl:

• Na⁺ is derived from NaOH, a base.
• Cl^- is derived from HCl, an acid.

This approach simplifies complex chemical processes by breaking them down into recognizable patterns. By understanding the source of each ion, you can determine the acid and base that contribute to the formation of a salt.

Chemical Formulas

Chemical formulas are shorthand notations that convey the composition of compounds using element symbols and numerical subscripts. Understanding chemical formulas helps in identifying the constituent ions in a salt and thereby the corresponding acid and base.

When interpreting chemical formulas:

• Identify the element symbols, which represent the types of atoms involved.
• Look for subscripts that indicate the number of each type of atom.

For KHCO₃, the formula indicates:

• One potassium (K) from KOH, the base component.
• The bicarbonate ion (HCO₃^-) comes from H₂CO₃, the acid component.

Chemical formulas provide insight into the makeup of the compound, enabling us to trace back to the simplest acid and base forms.

Salt Formation

Salt formation is a key concept in acid-base chemistry, describing the reaction of an acid and a base to form a salt and water. This is often depicted in what’s known as a neutralization reaction.

Neutralization reactions follow this general formula:

• Acid + Base → Salt + Water

Let's consider NH₄NO₂:

• The reaction involves NH₄OH from the acid side and HNO₂ from the base side.
• This combines to form the salt NH₄NO₂.

By understanding these reactions, you can predict the products formed and understand the underlying chemical processes. Recognizing the origins of the reacting acid and base provides clarity on how salts are constituted.