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Acid and Base reactions occur when an acid and base react with each other to neutralize acidic-basic properties and produce salt.
- When acid and base react, salt and water are formed.
- Acid-base reactions are double-replacement reactions in which ions exchange their positions.
- The reactions between acid and base are termed neutralization reactions.
- The ionic equation of neutralization is H+ (aq) + OH− (aq.) → H2O.
The general equation of acid-base reaction is given as:
Acid + Base → Salt + Water
Read More: NCERT Solution for Class 10 Science Chapter 2: Acids, Bases, and Salts
| Table of Content |
Key Terms: Acid, Base, Salt, Neutralization, Hydronium Ion, Proton, Hydrogen, Water
Acid and Base Reaction
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Acid and Base are combined and lead to the formation of salt and water as a product corresponding to acid and base.
- In an acid-base reaction, the (H+) cation of the acid combines with the anion of the base (OH-) to produce salt and water.
- The anion of the acid and the cation of the base combine to produce the salt.
For example,
Hydrochloric acid and sodium hydroxide combine to form table salt (NaCl) and water.
HCl + NaOH → NaCl + H2O
(acid) (base) (salt) (water)
To determine acid and base–
The acid and base in the reaction, count the number of hydrogen before and after the reaction.
- Acid donates hydrogen ions, hence in the reaction the hydrogen atom will decrease.
- Base accepts hydrogen ions, hence in the reaction, the hydrogen atom will increase.
Read More: Difference between Alkali and Base
Strong Acid and Strong Base Reaction
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Strong acids are those that easily release hydrogen ions (H+) when dissolved in water.
- A strong base readily releases (OH-) ions after being dissolved in the water.
- Strong acids and bases react and neutralize each other to form a salt.
The H+ ion combines with OH- to yield H2O.
H+ (aq) + OH- (aq) → 2H2O (l)
Weak Acid and Weak Base Reaction
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When a weak acid comes in a reaction with a weak base of an equivalent amount no complete neutralization takes place. Instead, an equilibrium is established between the acid, base, and products.
The concentrations of reactant and product depend on the equilibrium constant (Ka) of the reaction.
The general equation is given as:
AH + B ⇔ A− + BH+
Example:
Acetic acid releases (H+) atoms once dissolved in water, and yields acetate ions and hydronium ions.
CH3COOH (aq.) + H2O (l) ⇔ CH3COO−(aq.) + H3O+ (aq.)
(acetic acid) (acetate) (hydronium)
Also Read:
| Related Articles | ||
|---|---|---|
| Chemical Equilibrium | Ionic Equilibrium | Examples of Weak Acids |
| Displacement Reaction | Concentration of a Solution | Group 2 Elements |
Balancing Acid-Base Reaction
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Balancing acid and base reactions means equating the number of atoms in a molecule on both sides of the equation.
For example:
Consider the reaction between calcium hydroxide and phosphoric acid which produces insoluble calcium phosphate and water. The reaction is
H3PO4 (aq.) + Ca(OH)2 (aq.) → Ca3(PO4)2 (s) + H2O (l) …(1)
The above equation is unbalanced. Here, phosphate (PO4+) and calcium (Ca+) ions are not equal, so multiply reactants accordingly to balance.
2H3PO4 (aq.) + 3Ca(OH)2 (aq.) → Ca3(PO4)2 (s) + H2O (l) …(2)
Now, there are 6 oxygen atoms in Ca(OH)2. So, multiply H2O by 6 in eq(2) to balance O and H atoms.
2H3PO4 (aq.) + 3Ca(OH)2 (aq.) → Ca3(PO4)2 (s) + 6H2O (l)
The above chemical equation is balanced.
Read More: pH of Acids and Bases
Some Acid and Base Reaction
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Acid and a base react with each other to produce salt corresponding to their strength.
- Strong Acid and Strong Base Reaction –
- Hydrogen bromide reacts with magnesium hydroxide to produce magnesium bromide and water.
2HBr (aq.) + Mg(OH)2 (aq.) → MgBr2 (aq.) + 2H2O (l)
- Sulfuric acid reacts with calcium hydroxide to form calcium sulfate and 2 molecules of water.
Ca(OH)2 + H2SO4 → CaSO4 + 2H2O
- Sulfuric acid reacts with Calcium oxide and produces calcium sulfate and water.
H2SO4 (aq.) + CaO → CaSO4 + H2O
- Strong Acid and Weak Base –
- Hydrogen sulfate acid reacts with ammonia to form ammonium sulfate salt.
H2SO4 (aq.) + 2NH3 (aq.) → (NH4)2SO4 (aq.)
- Hydrobromic acid reacts with ammonia to give bromide and ammonium ions.
HBr + NH3 → Br− + NH4⊕
- Strong Base and Weak Acid –
- Sodium hydroxide and acetic acid react to form sodium acetate (salt).
NaOH (aq.) + CH3COOH (aq.) → CH3COONa (aq.) + H2O (l)
- Sodium hydroxide reacts with nitrous acid and gives sodium nitrite and water.
NaOH (aq.) + HNO2 (aq.) → NaNO2 (aq.) + H2O (l)
- Weak Acid and Weak Base –
Weak acids and bases react to form neutral salts. Such reactions are
- Acetic acid and ammonium hydroxide combine to produce ammonium ethanoate
CH3COOH + NH4OH → CH3COONH4 + H2O
- Ammonia reacts with hydrofluoric acid to produce ammonium salt (NH4+) and flooring (F−) ion.
HF (aq.) + NH3 (aq.) → NH4+ (aq.) + F− (aq.)
- Acetic acid dissolves in water to release acetate and hydronium ions.
CH3COOH (aq.) + H2O (l) → CH3COO− (aq) + H3O+
Read More: Hydrolysis
Acid and Base Reaction in Organic Chemistry
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According to Bronsted-Lowry theory, acids are a substance that donates a proton (H+) and a substance that accepts a proton is called a base.
Bronsted acid and base react with each other to produce a conjugate base of acid and conjugate acid of a base.
Example:
- Acetic acid reacts with methylamine to give acetate ion (conjugate base) and methylammonium ion (conjugate acid).
- Sodium hydride (NaH) reacts with Methanol (CH3OH) and produces the sodium salt of methanol (CH3O−Na+) and H2 (hydrogen gas).
CH3OH (aq.) + NaH (aq.) → CH3O−Na+ (aq.) + H2 (g)
Also Read:
| Related Articles | ||
|---|---|---|
| Lewis Acids | Acids, Bases, and Salts | Properties of Acids and Base |
| Acid Strength | Difference between Acid and Base | Examples of Weak Acids |
Things to Remember
- Acid and a base combine and yield salt and water as a byproduct.
- Acid releases hydronium ion (H3O+) and the base releases hydroxide ion (OH−) and they combine to form H2O.
- An equilibrium is established when weak acid and a weak base react.
- The acid-base reaction is used in digesting food, neutralizing stomach acid, and absorbing harmful SO2 gas.
Sample Questions
Ques. Strong acid and a strong base react to form ______. (1 Mark)
(a) A precipitate
(b) Salt and water
(c) Volatile product
(d) Insoluble salt and water
Ans. The correct option is (b)
A neutralization occurs when a strong acid and base combine and the product formed does not have characteristics of acid or base. Instead, water and a neutral salt are produced.
Ques. Using an example, explain the reaction between non-metallic oxide and base. Suggest the nature of non-metal oxides. (3 Marks)
Ans. Non-metallic oxide combines with a base to give salt and water. Consider the reaction between calcium hydroxide [Ca(OH)2] and carbon dioxide (CO2) which gives calcium carbonate [CaCO3] as a product.
CO2 + Ca(OH)2 → CaCO3 + H2O
Here, calcium hydroxide acts as a base and reacts with carbon dioxide to give salt and water.
Hence, oxides of non-metal are acidic.
Ques. Define neutralization reaction. Give two examples. (3 Marks)
Ans. A reaction where acid and base combine to neutralize each other and form salt and water as a product is called a neutralization reaction.
Examples:
(i) HCl + NaOH → NaCl + H2O
(ii) HCl + Mg(OH)2 → MgCl2 + 2H2O
Ques. Write the neutralization reaction between nitric acid and barium hydroxide. (4 Marks)
Ans. The neutralization reaction between nitric acid and barium hydroxide produces barium nitrate.
HNO3(aq.) + Ba(OH)2(aq.) → Ba(NO3)2(aq) + H2O
The above equation is not balanced. For balancing 2 molecules of HNO3 molecules will be required. Thus,
2HNO3(aq.) + Ba(OH)2(aq.) → Ba(NO3)2(aq) + 2H2O
Ques. Calcium oxide reacts with aqueous hydroiodic acid to form a soluble salt. Write a balanced equation. Also, find the number of HI molecules in the equation. (4 Marks)
Ans. Calcium oxide (CaO) reacts with hydroiodic acid and produces calcium iodide CaI2 (insoluble salt)
The equation is given:
CaO(s) + HI(aq) → CaI2 (aq) + H2O
In the equation, there are 2 iodine atoms in R.H.S and 1 in L.H.S. So, to balance the equation add 1 iodine atom to L.H.S.
Thus,
Balanced Equation ⇒ CaO(s) + 2HI(aq) → CaI2 (aq) + H2O
Number of HI molecules in the equation = 2
Ques. How acid and base reaction is effective in food preservation? (2 Marks)
Ans. The acid in the food is used to prevent or slow down the growth of an organism that causes disease or spoilage. Acid and base reactions can extend the shelf life of food keeping the nutrient content unchanged.
Ques. Write the ionic equation of the neutralization reaction. (1 Mark)
Ans. In the neutralization reaction, the net ionic equation is given by:
H+ (aq) + OH− (aq.) → H2O
H+ ion is released by acid and OH− by the base.
Ques. Write a balanced equation of zinc reacting with acid and base. (3 Marks)
Ans. The reaction of Zn with sulfuric acid is:
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2O(âÂÂ)
The reaction of Zn with sodium hydroxide is:
Zn(s) + 2NaOH(aq) → Na2ZnO2(aq) + H2O
Ques. Write some uses of acid and base reactions in our daily life. (3 Marks)
Ans. Some uses of acid and reactions are:
- Calcium oxide (CaO) can be used to neutralize the acidic soil which reduces the availability of nutrients.
- Hydrochloric acid (HCl) helps in digesting food.
- Antacids (bases) help neutralize stomach acid and prevent intestines from damage.
- Alkaline calcium hydroxide [Ca(OH)2] is used in absorbing harmful sulfur dioxide (SO2) gas which is produced from burning fossil fuel and power stations.
Ques. According to Bronsted Lowry, the acid and base reactions are _______ reactions. (1 Mark)
(a) Electron transfer
(b) Proton transfer
(c) Electrolytic
(d) Nuclear transfer
Ans. The correct option is (b)
Explanation: According to Bronsted Lowry's theory, acid is the substance that donates (H+) ions, and base accepts (H+). In an acid-base reaction, proton ion (H+) is transferred from acid to base. Hence, acid-base reactions are proton transfer reactions.
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