Acids and bases exhibit a wide range of physical and chemical properties that allow us to identify and differentiate them. These properties are observable in laboratory reactions and in daily-life applications. Understanding their properties is essential in fields ranging from industrial chemistry to biology and medicine.
Physical Properties of Acids
- Sour taste: Most acids taste sour (e.g., citric acid in lemon).
- Corrosive nature: Strong acids can corrode metals and skin.
- Turns blue litmus red: A classic test for acidic substances.
- Conductivity: Acids ionize in water and conduct electricity.
- pH value: Acids have pH less than 7.
Chemical Properties of Acids
- Reaction with metals: Acids react with reactive metals (like Zn, Mg) to produce hydrogen gas.
Example: Zn + 2HCl → ZnCl₂ + H₂↑ - Reaction with carbonates: Produces salt, water, and CO₂.
Example: HCl + Na₂CO₃ → NaCl + H₂O + CO₂ - Neutralization: Acids neutralize bases to form salt and water.
Example: HCl + NaOH → NaCl + H₂O
Physical Properties of Bases
- Bitter taste: Most bases are bitter (e.g., baking soda).
- Soapy feel: Bases feel slippery to touch.
- Turns red litmus blue: A classic indicator test for bases.
- Conductivity: Bases dissociate in water and conduct electricity.
- pH value: Bases have pH more than 7.
Chemical Properties of Bases
- Reaction with acids: Neutralization to form salt and water.
- Reaction with ammonium salts: Releases ammonia gas.
Example: NaOH + NH₄Cl → NaCl + NH₃↑ + H₂O - Reaction with metal salts: Can precipitate metal hydroxides.
Example: NaOH + FeCl₃ → Fe(OH)₃↓ + NaCl
Indicators and pH Range of Acids and Bases
- Litmus: Acid turns blue to red; base turns red to blue.
- Phenolphthalein: Colorless in acid, pink in base.
- Methyl orange: Red in acid, yellow in base.
Conclusion
Acids and bases show distinct properties that help in their identification and application. Their reactivity with metals, carbonates, and salts along with changes in pH and indicators make them essential in chemistry, biology, environmental science, and industrial processes.
Quiz: Properties of Acids and Bases
Q1: Which of the following turns blue litmus red?
A) NaOH
B) NH₄OH
C) HCl
D) NaCl
Answer: C) HCl
Explanation: Acids turn blue litmus red.
Q2: What gas is evolved when acids react with metals?
A) CO₂
B) O₂
C) H₂
D) N₂
Answer: C) H₂
Explanation: Acids release hydrogen gas with metals.
Q3: Which is a property of bases?
A) Sour taste
B) Turns red litmus blue
C) Reacts with carbonates
D) Produces hydrogen with Zn
Answer: B) Turns red litmus blue.
Q4: Which indicator is pink in a basic solution?
A) Methyl orange
B) Phenolphthalein
C) Litmus
D) Bromothymol blue
Answer: B) Phenolphthalein.
Q5: What is formed when an acid reacts with a base?
A) Water only
B) Salt only
C) Salt and water
D) Water and gas
Answer: C) Salt and water.
FAQs: Properties of Acids and Bases
Q1. Why do acids conduct electricity?
Acids release H⁺ ions in water, which act as charge carriers and conduct electricity.
Q2. Why are bases slippery in touch?
Bases react with the natural oils of skin forming soap-like compounds, giving a soapy feel.
Q3. Which acid is commonly used in car batteries?
Sulfuric acid (H₂SO₄) is used in lead-acid batteries.
Q4. Can a substance act as both acid and base?
Yes, such compounds are called amphoteric (e.g., water, Al(OH)₃).
Read also: Classification of Acids and Bases |
Reference: Britannica: Acid-Base Reactions
