• Engineering and Architecture
  • Management and Business Administration
  • Medicine and Allied Sciences
  • Law
  • Animation and Design
  • Media, Mass Communication and Journalism
  • Finance & Accounts
  • Computer Application and IT
  • Pharmacy
  • Hospitality and Tourism
  • Competition
  • School
  • Study Abroad
  • Arts, Commerce & Sciences
  • Learn
  • Online Courses and Certifications
Weak Acid Examples - Definition, Important of Weak Acids, FAQs

Weak Acid Examples - Definition, Important of Weak Acids, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:45 PM IST

Acids

Acids are compounds that can donate a proton (hydrogen ion) to another material by dissolving in water and producing H+ ions. Acids are distinguished by their sour flavour. Acids turn blue litmus red by donating H+ ions and remaining favourable even after losing H+ ions.

Strong acid and weak acid

Weak acids can only be partially ionized in their solutions, but strong acids can be fully ionized when dissolved in water. In comparison to strong acids, weak acids are more routinely used. They are prevalent in everyday life, such as vinegar and lemon juice. When they're dissolved in water, the concentration of the weak acid and its constituent ions reach a point of equilibrium. Acids, bases and Salts can be read in detail from here.

This Story also Contains
  1. Acids
  2. Strong acid and weak acid
  3. What is a weak acid?
  4. Weak mineral acid
Weak Acid Examples - Definition, Important of Weak Acids, FAQs
Weak Acid Examples - Definition, Important of Weak Acids, FAQs

Also, check-

To get more content related to NCERT Exemplar Solutions for class 11th and class 12th. Students can refer to the links given below:

What is a weak acid?

Weak acid definition- A weak acid is an acid that partially dissociates into its constituent ions when dissolved in water. Some weak acids list or weak acid names are given below.

Weak acid examples

  • Formic acid (HCOOH)

  • Acetic acid (CH3COOH)

  • Benzoic acid (C6H5COOH)

  • Oxalic acid (C2H2O4)

  • Hydrofluoric acid (HF)

  • Nitrous acid (HNO2)

  • Sulfurous acid (H2SO3)

  • Phosphoric acid (H3PO4)

Some of the examples of weak acids can be briefly explained as below;

1. Formic Acid.

One of the most basic carboxylic acids is formic acid, commonly known as methanoic acid. HCOOH is the chemical formula for this substance. Formic acid is a weak acid that is found naturally inside the bodies of some ants. Formic acid occurs as a colourless liquid (with occasional vapours) under ordinary temperature and pressure conditions. The density of this chemical is 1.22 grams per millilitre. With water, this weak acid is known to generate a miscible combination.

The pKa value of this weak acid is found to be 3.745. Formate is the conjugate base that results from the deprotonation of formic acid. Formic acid also creates miscible compositions with a variety of other organic solvents, including acetone, glycerol, ethanol, and methanol. Furthermore, it is known that this molecule is somewhat soluble in aromatic chemicals like benzene and toluene. Formic acid has a molecular mass of 46.025 grams per mole.

2. Acetic Acid

Acetic acid, commonly known as ethanoic acid, is a weak acid having the formula CH3COOH. It's the active ingredient in vinegar, which is a 4% to 7% acetic acid solution in water. When dissolved in water, acetic acid only partially dissociates into its constituent ions, making it a weak acid. It's worth noting, too, that concentrated acetic acid is known to corrode human skin. This weak acid is reported to exist as a colourless liquid with a strong, vinegar-like odour at typical temperature and pressure conditions.

Acetic acid has a density of 1.049 grams per cubic centimetre when it is liquid. Solid acetic acid, on the other hand, is known to have a higher density, measuring 1.27 grams per cubic centimetre. Acetic acid's melting point is usually between 16 and 17 degrees Celsius. Acetic acid's boiling point is also reported to range between 118 and 110 degrees Celsius. With water, this weak acid is known to generate miscible combinations.

Related topics link,
NEET Highest Scoring Chapters & Topics
This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.
Download EBook

3. Oxalic Acid

Oxalic acid (C2H2O4) is a widely used weak acid. Under typical temperature and pressure circumstances, this organic compound exists as a crystalline solid that is white in colour. The acidity of this molecule is significantly higher than that of acetic acid. The molar mass of the dihydrate of this chemical molecule is 126.06 grams per mole.

Under STP, the density of this chemical is reported to be 1.9 grams per cubic centimeter (in its anhydrous state). The melting point of anhydrous oxalic acid is approximately 190 degrees Celsius. This organic acid is known to be relatively water soluble. Oxalic acid is soluble in water at a temperature of 20 degrees Celsius and has a solubility of 90 to 100 grams per liter.

4. Benzoic Acid

C6H5COOH is the chemical formula for benzoic acid, an aromatic carboxylic acid. This substance is a weak acid that can be found in various plants, as well as gum benzoin. Preservatives made from the salts of this weak acid are frequently utilized in the food sector. This chemical has a molecular mass of 122.123 grams per mole. Benzoic acid is known to exist as a crystalline solid with no distinguishable colour at typical temperature and pressure conditions. Benzoic acid has a faintly pleasant odour due to the presence of an aromatic system in the substance.

The density of benzoic acid is approximately 1.26 grams per cubic centimeter under typical temperature and pressure conditions. It should be noted, however, that the solubility of benzoic acid in the water rises with increasing temperature. The solubility of benzoic acid in water increases to 56.31 grams per liter at a temperature of 100 degrees Celsius.

Also Read:

Below are some of the NCERT solutions and NCERT exemplar solutions for Class 12th Chemistry.

5. Hydrofluoric Acid

Hydrofluoric acid (HF) is another example of a weak acid. When dissolved in water, this molecule does not entirely dissociate into hydrogen and fluoride ions, making it a weak acid. However, it is vital to keep in mind that hydrofluoric acid is toxic to humans and that contact with human skin can result in severe burns. A solution of hydrogen fluoride in water (which produces hydrofluoric acid) is colourless. The density of a 48% HF solution in water is estimated to be 1.15 grams per milliliter. The pKa value of hydrofluoric acid is found to be3.17.

Weak mineral acid

Weak mineral acid is formed from more than one inorganic compounds. Weak mineral acid example is boric acid.

Also read -

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. Define weak acid.

Weak acid is an acid which partially dissociates into its constituent ions when dissolved in water. In other words weak acid dissociation is partial.

2. What are the important weak acids?
Some examples of weak acids are Oxalic acid, Ethanoic acid (Acetic acid), Ascorbic acid (Vitamin C), Phosphoric Acid, Nitrous acid, Methanoic acid (Formic Acid),and Water

3. What is the difference between a strong acid and a weak acid?

A strong acid is one that entirely ionizes in an aqueous solution. When dissolved in water, it always loses a proton (H+). A weak acid is one that only partially ionizes in a solution. When dissolved in water, it hardly gives out a few of its (H+) atoms.

4. What can weak acids be used for?
Weak acids are effective antimicrobials in their protonated form hence they are mostly used in the preservation of acid foods
5. What are the uses of acetic acid?

It is an example of a weak acid that is utilized in cleaning products used to clean the floors and cutlery, etc. It's used to improve the flavour of meals. Vinegar is a frequent name for acetic acid. This weak acid aids in the removal of stains from the woodwork, furniture, and carpets.

6. What are the major uses of phosphoric acid?

Phosphoric acid is an example of a weak acid that has a wide range of applications. Many soft drinks contain phosphoric acid as a primary ingredient. Phosphoric acid is also utilized in the fertilizer and detergent manufacturing industries.

7. Is formic acid a strong acid?

No, formic acid is a weak acid.

8. Which is weak acid acetic acid or hydrochloric acid?

 Acetic acid is a weak acid and hydrochloric acid is a strong acid.

9. What is HF compound name?

Hydrogen fluoride

10. How do weak acids interact with metals compared to strong acids?
Weak acids generally react more slowly and less vigorously with metals compared to strong acids. While strong acids can rapidly dissolve many metals, weak acids may only react with more reactive metals or require heat to initiate the reaction. This difference is due to the lower concentration of hydrogen ions available in weak acid solutions.
11. How do weak acids behave in titrations?
In titrations, weak acids produce a gradual change in pH as a strong base is added, resulting in a curved titration graph. The equivalence point occurs at a pH above 7, and the solution at this point contains the salt of the weak acid and its conjugate base. The gradual pH change allows for the use of indicators to determine the endpoint of the titration.
12. What is the significance of pKa in understanding weak acids?
pKa is the negative logarithm of the acid dissociation constant (Ka). It provides a convenient way to express and compare acid strengths. A lower pKa indicates a stronger acid. The pKa value is particularly useful because:
13. What is the common ion effect, and how does it affect weak acids?
The common ion effect occurs when an ion that is part of the equilibrium of a weak acid is added to the solution from another source. For example, adding sodium acetate (which dissociates to form acetate ions) to a solution of acetic acid will suppress the dissociation of the acid. This effect reduces the concentration of hydrogen ions, increasing the pH of the solution.
14. What is the role of weak acids in analytical chemistry?
Weak acids are important in analytical chemistry for several reasons:
15. Can you name some common weak acids found in everyday life?
Common weak acids in everyday life include:
16. What is the Ka value, and how does it relate to weak acids?
Ka, or the acid dissociation constant, is a measure of an acid's strength. For weak acids, Ka values are typically less than 1. A lower Ka value indicates a weaker acid, as it means less dissociation occurs. The Ka value is used in calculations to determine the pH and concentration of ions in weak acid solutions.
17. Why are weak acids important in biological systems?
Weak acids play crucial roles in biological systems because they can act as buffers, helping to maintain stable pH levels in cells and bodily fluids. They can donate or accept protons as needed, which is essential for many biochemical reactions and maintaining homeostasis in living organisms.
18. How do weak acids contribute to buffer solutions?
Weak acids, along with their conjugate bases, form buffer solutions. These solutions resist changes in pH when small amounts of acid or base are added. The weak acid can neutralize added bases by donating protons, while its conjugate base can neutralize added acids by accepting protons, maintaining a relatively stable pH.
19. How does temperature affect the dissociation of weak acids?
Temperature generally increases the dissociation of weak acids. As temperature rises, more energy is available for molecules to overcome the energy barrier for dissociation. This leads to a slight increase in the acid dissociation constant (Ka) and, consequently, a small decrease in pH of the weak acid solution at higher temperatures.
20. What defines a weak acid?
A weak acid is a substance that only partially dissociates in water, releasing a small amount of hydrogen ions (H+). Unlike strong acids, weak acids do not completely break apart in solution, maintaining an equilibrium between the acid molecules and their ions.
21. How does the strength of a weak acid compare to a strong acid?
Weak acids have a lower degree of dissociation compared to strong acids. This means they produce fewer hydrogen ions in solution, resulting in a higher pH than strong acids at the same concentration. Weak acids typically have a pH between 2 and 7, while strong acids have a pH below 2.
22. What is the difference between a weak acid and a dilute acid?
A weak acid is defined by its incomplete dissociation in water, regardless of concentration. A dilute acid, on the other hand, refers to an acid solution with a low concentration of acid molecules, regardless of whether it's a strong or weak acid. A weak acid can be concentrated or dilute, but it will always have limited dissociation.
23. What is meant by the term "percent dissociation" for weak acids?
Percent dissociation refers to the proportion of weak acid molecules that have dissociated into ions in solution. It is calculated as:
24. How does the concentration of a weak acid affect its pH?
As the concentration of a weak acid increases, its pH decreases, but not linearly. Due to the equilibrium nature of weak acid dissociation, doubling the concentration does not halve the pH. Instead, the relationship follows a logarithmic pattern, with smaller pH changes for concentration increases in more concentrated solutions.
25. What is the Henderson-Hasselbalch equation, and how is it used with weak acids?
The Henderson-Hasselbalch equation is used to calculate the pH of buffer solutions containing weak acids and their conjugate bases. It relates pH to the pKa of the weak acid and the ratio of the concentrations of the acid and its conjugate base:
26. What is the relationship between weak acids and their salts in solution?
When a salt of a weak acid dissolves in water, it undergoes hydrolysis, which affects the pH of the solution. The anion of the weak acid acts as a base, accepting protons from water molecules. This results in an increase in OH- ions, making the solution slightly basic. For example, sodium acetate in water produces a basic solution due to the hydrolysis of the acetate ion.
27. How do weak acids interact with proteins?
Weak acids can interact with proteins in several ways:
28. What is the concept of acid rain, and how do weak acids contribute to it?
Acid rain refers to precipitation with increased acidity due to atmospheric pollutants:
29. What is the role of weak acids in organic synthesis?
Weak acids are important in organic synthesis as they can:
30. What is the concept of conjugate acid-base pairs in relation to weak acids?
A conjugate acid-base pair consists of two species that differ by a single proton. When a weak acid (HA) dissociates, it forms its conjugate base (A-):
31. How do polyprotic weak acids differ from monoprotic weak acids?
Polyprotic weak acids can donate multiple protons, while monoprotic weak acids can only donate one. Polyprotic acids, like phosphoric acid (H3PO4), have multiple dissociation steps, each with its own Ka value. This results in more complex equilibria and titration curves compared to monoprotic acids. The strength of each successive dissociation typically decreases.
32. How do weak acids contribute to acid rain?
While strong acids like sulfuric and nitric acids are primary contributors to acid rain, weak acids also play a role. Carbonic acid, formed when carbon dioxide dissolves in water, is a weak acid that contributes to the natural acidity of rainwater. Additionally, organic acids from the decomposition of vegetation can contribute to the acidity of rain in forested areas.
33. How do weak acids participate in buffer systems in the human body?
Weak acids are crucial components of buffer systems in the human body. For example:
34. How do weak acids behave in non-aqueous solvents?
The behavior of weak acids can change significantly in non-aqueous solvents. Factors that influence their behavior include:
35. What is the significance of weak acids in food preservation?
Weak acids are widely used in food preservation due to their ability to inhibit microbial growth. They function by:
36. How do weak acids contribute to the taste of foods?
Weak acids play a crucial role in the taste profile of many foods:
37. What is the concept of Lewis acids, and how do they relate to weak Brønsted-Lowry acids?
Lewis acids are electron pair acceptors, while Brønsted-Lowry acids are proton donors. Some compounds can act as both:
38. How do weak organic acids differ from weak inorganic acids?
Weak organic acids and weak inorganic acids differ in several aspects:
39. What is the importance of weak acids in environmental chemistry?
Weak acids play crucial roles in environmental chemistry:
40. How do weak acids participate in esterification reactions?
Weak acids, particularly carboxylic acids, are key reactants in esterification:
41. What is the role of weak acids in chemical equilibrium studies?
Weak acids are ideal for studying chemical equilibrium because:
42. How do weak acids contribute to the chemistry of carbonated beverages?
Weak acids, primarily carbonic acid, are fundamental to carbonated beverages:
43. What is the significance of weak acids in soil chemistry?
Weak acids are important in soil chemistry for several reasons:
44. How do weak acids interact with bases in neutralization reactions?
When weak acids react with bases:
45. What is the role of weak acids in pharmaceutical formulations?
Weak acids are important in pharmaceuticals for several reasons:
46. How do weak acids contribute to the formation of coordination compounds?
Weak acids can act as ligands in coordination compounds:
47. What is the importance of weak acids in biochemical pathways?
Weak acids play crucial roles in biochemical pathways:
48. How do weak acids affect the solubility of other substances?
Weak acids can influence the solubility of other substances in several ways:
49. How do weak acids participate in redox reactions?
Weak acids can be involved in redox reactions in several ways:

Also Read

Alkoxymercuration Mechanism: Reaction, Example, Applications

02 Jul'25 05:26 PM

Aldol Condensation Questions: MCQs with Answers

02 Jul'25 05:26 PM

Aldehydes Ketones: Overview, Reactions, Physical Properties, Uses, FAQs

02 Jul'25 05:26 PM

Acetylation: Overview, Reaction, Mechanism, FAQs

02 Jul'25 05:25 PM

Acetal Explanation: Acetal Structures, Synthesis, Uses, FAQs

02 Jul'25 05:25 PM

Aldehyde Group: Overview, Structure, General Properties, Synthesis, Uses

02 Jul'25 05:25 PM

Ammonium Oxalate: Introduction, Molecular Weight, Properties, Formula, Uses

02 Jul'25 05:14 PM

Acid Anhydrides- Definition and Meaning of Acid anhydride, Synthesis, Chemical Properties

02 Jul'25 05:13 PM

Acetate: Structure, Properties, Definition, Formula & Structure

02 Jul'25 05:12 PM

Acetonitrile: Properties, Reactions, Uses Of Acetonitrile

02 Jul'25 05:10 PM

Articles

Back to top