Question

Write the formulas of the conjugate bases of the (b) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (c) \(\mathrm{H}_{2} \mathrm{~S},\) following acids: (a) \(\mathrm{HNO}_{2}\), (d) \(\mathrm{HCN}\) (e) \(\mathrm{HCOOH}\) (formic acid).

Short answer

The conjugate bases are (a) \(\mathrm{NO}_2^-\), (b) \(\mathrm{HSO}_4^-\), (c) \(\mathrm{HS}^-\), (d) \(\mathrm{CN}^-\), and (e) \(\mathrm{HCOO}^-\).

Step-by-step solution

Understanding Conjugate Bases

The conjugate base of an acid is formed when the acid donates a proton (\(\text{H}^+\)). For any acid \(\text{HA}\), the conjugate base is \(\text{A}^-\). In each acid, we will replace \(\text{H}\) with its negative counterpart.

(a) Find the Conjugate Base of \(\mathrm{HNO}_2\)

The acid \(\mathrm{HNO}_2\) donates a proton to form its conjugate base \(\mathrm{NO}_2^-\).

(b) Find the Conjugate Base of \(\mathrm{H}_2\mathrm{SO}_4\)

\(\mathrm{H}_2\mathrm{SO}_4\) can donate a proton to form the bisulfate ion \(\mathrm{HSO}_4^-\) as its conjugate base, which can further donate another proton to form \(\mathrm{SO}_4^{2-}\). The conjugate base after losing one proton is \(\mathrm{HSO}_4^-\).

(c) Find the Conjugate Base of \(\mathrm{H}_2\mathrm{S}\)

\(\mathrm{H}_2\mathrm{S}\) donates a proton to form \(\mathrm{HS}^-\), which acts as the conjugate base. \(\mathrm{HS}^-\) can further donate a proton to form \(\mathrm{S}^{2-}\), but after losing one proton, it is \(\mathrm{HS}^-\).

(d) Find the Conjugate Base of \(\mathrm{HCN}\)

The conjugate base of \(\mathrm{HCN}\) is formed by the removal of a hydrogen ion, resulting in \(\mathrm{CN}^-\).

(e) Find the Conjugate Base of \(\mathrm{HCOOH}\) (Formic Acid)

Formic acid \(\mathrm{HCOOH}\) loses a proton to form its conjugate base \(\mathrm{HCOO}^-\).

Key concepts

Proton Donation

In chemistry, when we talk about acids giving away their protons, we're referring to a process called proton donation. An acid is a substance that can donate a hydrogen ion (\(\text{H}^+\)). This process is crucial because it leads to the formation of a conjugate base. In simple terms, when an acid molecule gives up a proton, what's left is called its conjugate base.

• General Rule: An acid becomes a conjugate base after donating a proton.
• Example: If we take \(\mathrm{HCl}\), once it gives away a proton, we are left with \(\mathrm{Cl}^-\), which is the conjugate base.

This concept is fundamental for understanding how acids and bases interact in various chemical reactions.

Acid-Base Reactions

Acid-base reactions are chemical processes where an acid donates a proton to a base. These reactions are essential for many biological and chemical systems. Imagine acids as proton donors and bases as proton acceptors. In a reaction, when an acid gives up its proton, it transforms into a conjugate base, while the base turns into its conjugate acid.

• Reaction Example: When \(\mathrm{HCl}\) (an acid) reacts with \(\mathrm{NaOH}\) (a base), it forms water and sodium chloride. \(\mathrm{HCl} + \mathrm{NaOH} \rightarrow \mathrm{H_2O} + \mathrm{NaCl}\)
• Outcome: The proton from the acid \(\mathrm{HCl}\) is transferred to the base \(\mathrm{NaOH}\), showcasing the acid-base behavior.

Understanding these reactions helps in predicting the products and behavior of many chemical systems.

Conjugate Acid-Base Pairs

In any acid-base reaction, we deal with conjugate acid-base pairs. These pairs consist of an acid and its corresponding conjugate base or a base and its conjugate acid. Recognizing these pairs is necessary because they show the transformation process between donors and acceptors of protons.

• Acid Example: \(\mathrm{HNO_2}\) (acid) and \(\mathrm{NO_2^-}\) (conjugate base).
• Base Example: Let's consider the base \(\mathrm{NH_3}\), which converts to \(\mathrm{NH_4^+}\) when it accepts a proton, forming a conjugate acid.

These pairs are valuable for predicting the direction of a reaction and understanding reaction mechanisms.

Chemical Formulas

Chemical formulas are symbolic representations of chemical compounds. They show the elements present and the number of atoms involved. For acids and their conjugate bases, understanding their formulas is crucial for identifying the changes that occur during proton donation.

• Formula Basics: A typical chemical formula includes element symbols and subscripts showing how many of each element are present. For example, \(\mathrm{H_2SO_4}\) contains two hydrogen (H), one sulfur (S), and four oxygen (O) atoms.
• Conjugate Base Insight: The formula for the acid \(\mathrm{H_2SO_4}\) becomes \(\mathrm{HSO_4^-}\) after losing one proton.

Understanding these formulas helps in identifying acids, bases, and their corresponding reactions.

Ion Formation

When acids donate protons, ions are often formed. An ion is an atom or molecule that has become charged due to the loss or gain of electrons. In acid-base chemistry, the loss of a proton often leads to the formation of an anion, which is negatively charged.

• Ion Basics: An acid, like \(\mathrm{HCN}\), forms the ion \(\mathrm{CN}^-\) after donating a proton. The negative charge indicates it has one extra electron.
• Results of Ion Formation: This transformation is crucial, as the ions formed during reactions drive chemical balance and reactivity in solutions.

Grasping ion formation is essential for understanding the electrical properties and behaviors of chemical solutions.