The distinction between the characteristics of acids and bases is generally based on taste and feel. The acids are sour and the bases are bitter in taste. The bases felt soapy to the touch.
Arrhenius’s concept of acid and base produces a deep chemical understanding of their properties. The pH of the acids is less than 7 whereas the pH of bases is greater than 7.
An acid is a molecule or an ion that is capable to donate a proton known as Bronsted-Lowry acid. It can also be defined as accepters of electron pairs known as Lewis acids. In comparison, bases are substances that can donate electron pairs and accept protons.
Physical Characteristics of acids and bases
Properties of acid
- The acids have a sour taste.
- They can produce a stinging sensation on the broken skin.
- They are soluble in water.
- The acids turn blue litmus red.
- The pH of the acidic solution is less than seven.
Properties of bases
- The bases have a bitter taste.
- They are slippery in touch.
- These are colorless except hydroxide of iron and copper.
- Some bases are soluble in water.
- They turn red litmus blue.
- The pH of the basic solution is greater than seven.
Chemical characteristics of acids and bases
The reaction of acid and bases with metals
The reaction of the acid and alkalis with metals is quite similar to the neutralization reaction. This is because it produces salt. However, the only difference is that the hydrogen gas is liberated instead of water. For example, the reaction between magnesium and hydrochloric acid yield magnesium chloride and hydrogen gas.
2HCl + Mg → MgCl2 + H2↑
Alkalis such as NaOH react with zinc (Zn) to produce salt and hydrogen gas.
2NaOH + Zn → Na2ZnO2 + H2↑
The reaction of carbonates and bicarbonates with acids
Acids react with carbonates and bicarbonates to produce salt, water, and carbon dioxide. However, this reaction determines whether the unknown solution is basic or acidic. So, when a carbonate is added to a solution and effervescence is observed, the solution will be acidic.
CaCO3 + 2HCl → CaCl2 + H2O + CO2↑
In addition to it, the reaction between bicarbonate and acid is similar and represented by the following:
NaHCO3 + HCl → NaCl + H2O + CO2↑
However, bases do not react with metal carbonates. This is because metal carbonates are also bases.
Neutralization Reaction
When acids and bases react with each other. They formed salt and water. This reaction is known as the neutralization reaction. The general equation for this reaction is given below:
NaOH + HCl → NaCl + H2O ΔHr=-57 KJmol-1
The pH of acid and bases
pH is the hydrogen ion concentration expressed in the exponent form. pH scale ranges from 1 to 14. The lower the pH, the more solution will be more acidic. However, when the pH of the solution is greater. The solution will be basic. To check the pH of the solution we use special chemical compounds known as indicators. They change color in acidic and basic solutions. For example, litmus turns red in acidic. Whereas it turns blue in basic. Similarly, phenolphthalein is colorless in acidic but pink in basic solution.
Conductivity
The acids and water-soluble bases (alkali) can conduct electricity in an aqueous solution. This is because, in an aqueous solution, they contain dissolved ions. Therefore, acids and bases are electrolytes. It is important to note that strong acids and bases are strong electrolytes. This is because they dissociate completely into ions. However, weak acids and bases are weak electrolytes due to less dissociation.
Uses of acids and bases
There are the following uses for acids and bases:
Uses of acids
- Sulphuric acid is used in the batteries.
- Phosphoric acid is used in many soft drinks.
- Boric acid is used for eye wash, mouth wash. as an antiseptic, etc.
- Vinegar, a dilute solution of acetic acid is used as a flavoring in food.
- A mixture of hydrochloric acid and nitric acid which is known as aqua regia is used in washing the glassware. This can dissolve metals like gold (Au) and platinum (Pt) by forming their chlorides.
- Citric acid can be used in the preservation of food.
Uses of bases
- Calcium hydroxide which is known as slaked lime is used in the formation of bleaching powder.
- Ammonium hydroxide is a very important reagent for the detection of some basic radicals.
- Slaked lime can be used to neutralize acidic soil.
- Sodium hydroxide (NaOH) can be used in the manufacturing of soaps.
- Potassium hydroxide is used in the batteries.
- Milk of magnesia is used as a medicine for the acidity of the stomach.
Characteristics of acids and bases: Key Takeaways
Related Resources
- Lewis acid vs Lewis base
- HSAB theory: Hard and Soft, Acids and Bases
- Ascorbic vs. Citric Acids: Which one is What.
Concepts Berg
What is a polyprotic acid?
Those acids which have the capability to lose more than one proton per molecule is known as polyprotic acid. For example, sulphuric acid, sulfurous acid, etc.
What are examples of acids?
Examples of some acids are given below:
- Hydrochloric acid
- Sulphuric acid
- Nitric acid
- Perchloric acid
- Formic acid
- acetic acid
- lactic acid
What are examples of bases?
Examples of some bases are given below:
- Potassium hydroxide
- sodium hydroxide
- lithium hydroxide
- ammonia
- magnesium hydroxide
- calcium hydroxide
Is pure water basic or acidic?
Pure water is amphoteric in nature. Hence, it means that it can act as both acid and water.
What are some common attributes of bases?
The bases have the following attributes:
- Bases have a bitter taste.
- They have the soapy touch
- They have a pH greater than 7
- They turn red litmus to blue
What is the concept of acids and bases?
Acids are a substance that has the capability to donate protons. Whereas bases are substances that have the ability to accept protons.
What is the reaction of acid and bases on litmus paper?
The acids turn blue litmus to red. Whereas the base turns red litmus blue.
References
- Advanced Organic Chemistry fifth edition by Francis A. Carey (University of Virginia) and Richard J. Sundberg
