Ionization Of Acids And Bases MCQ Quiz in मल्याळम - Objective Question with Answer for Ionization Of Acids And Bases - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Correct answer: 2)

Concept:

• The acidic or basic strength of any solution can be described on the basis of pH value.
• pH can be expressed as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution.
• pH can be expressed as, pH=-log[aH+]

• The pKa value is the negative base -10 logarithm of the acid dissociation constant (Ka) of a solution. The higher is the value of pKa the lower will be the acid strength.

• An electron-withdrawing substituent decreases electron density, stabilizes the anion, and thus, increases the acidity of carboxylic acid.

• An electron-releasing substituent increases electron density (negative charge) destabilize the anion and thus, decreases acidity. 
• The effect of substituent, on aromatic acid, in fact, is determined by their inductive and resonance effect.
• Inductive effect affects all positions, i.e., o-, m-, and p-, however, resonance effect affects only o- and p- positions.

Explanation:

• In the case of o-, m-, and p-nitro benzoic acids, the -NO₂ group exerts a greater electron-withdrawing effect when present in the o- and p- positions.
• So, o- and p- nitrobenzoic acids are the strongest acids.
• the smaller the pK_a value, the stronger the acid.
• 

Conclusion:

Thus, the correct decreasing order of acidic strength (i) > (ii) > (iii).

The correct answer is 

Concept:-

• Brönsted-Lowry Acid-Base Theory: According to this theory, an acid is a substance that can donate a proton (H+), and a base is a substance that can accept a proton. In an acid-base reaction, an acid loses a proton to become a conjugate base, and a base gains a proton to become a conjugate acid.
• Conjugate Acid-Base Pairs: These are pairs of compounds that differ from each other by one proton. For an acid, the conjugate base is the compound formed when the acid donates (loses) a proton. For a base, the conjugate acid is the compound formed when the base accepts (gains) a proton.
• Strong and Weak Acids: Strong acids are those that almost completely dissociate into their ions in water, increasing the concentration of H⁺ ions drastically. Weak acids partially dissociate, providing fewer H⁺ ions in a solution. Strong acids, like H₂SO₄, will have weak conjugate bases because they've lost the ability to regain the proton they once donated. Conversely, weak acids like HF have strong conjugate bases.

Explanation:-

HF: This is a weak acid. When it donates a proton (H+), it forms F-, its conjugate base. So F- is correct.

H₂SO₄ (Sulfuric Acid): This is a strong acid, and it can donate two protons. When it donates one proton, it forms HSO₄^-, and this is its conjugate base, not H₂SO₃. So HSO₄^- is correct.

HCO₃^- (Bicarbonate Ion): It acts as an acid and when it donates one proton, it forms CO₃ ^2- (carbonate ion), which is the conjugate base. So CO₃ ^2- is correct.

Hence, the correct conjugate bases are F^-, HSO₄^-, and CO₃ ^2-, which corresponds to answer 1) F⁻,HSO⁻₄,CO₃^2-

Concept: 

Ionization Constant: 

• In a solution or liquid, the equilibrium between ions and non-ionized molecules determines a constant known as an ionization constant (with the symbol K).
• It is either the ratio of the product of concentration to the reactant or the ratio of products and reactants increased to the proper stoichiometric powers.
• A dissociation constant is another name for an ionization constant. 

Let's assume a general reaction:

\(HA\;+\;H_{2}O\;\rightleftharpoons \;A^{-}\;+\;H_{3}O^{+}\)

\(K\;=\;\dfrac{[A^{-}][H_{3}O^{+}]}{[HA]}\)

For acid, the dissociation constant is represented by \(K_{a}\) ,and for the base, it is denoted by \(K_{b}\).

A hydrolysis reaction's equilibrium constant is known as the hydrolysis constant. It is represented by \(K_{h}\).

Explanation:

Ionization constant of acetic acid \(K_{a}\;=\;1.8\times 10^{-5}\)

Sodium acetate with formula \(CH_{3}COO^{-}Na^{+}\) does not react with water, only its anionic part undergoes hydrolysis. 

\(CH_{3}COO^{-}\;+\;H_{2}O\rightleftharpoons \;CH_{3}COOH\;+\;OH^{-}\)

The hydrolysis constant for this reaction is:

\(K_{h}\;=\;\dfrac{[CH_{3}COOH][OH^{-}]}{[CH_{3}COO^{-}]}\).......... (1)

Now, the dissociation equation for acetic acid is:

\(CH_{3}COOH\;\rightleftharpoons \;CH_{3}COO^{-}\;+\;H^{+}\)

\(K_{a}\;=\;\dfrac{[CH_{3}COO^{-}][H^{+}]}{[CH_{3}COOH]}\)...... (2)

Now, multiplying equations (1) and (2)

\(K_{h}\times K_{a}\;=\;\dfrac{[CH_{3}COOH][OH^{-}]}{[CH_{3}COO^{-}]}\times\dfrac{[CH_{3}COO^{-}][H^{+}]}{[CH_{3}COOH]}\)

\(K_{h}\times K_{a}\;=\;[OH^{-}]\times [H^{+}]\)

\([OH^{-}][H^{+}]\;=\;K_{w}\)

So, \({K_{h}\times K_{a}\;=\;K_{w}}\) .......... (3)

where, \(K_{w}\) is the ion product constant of water whose value at \(10^{-14}\).

Now substitute the values in equation (3)

\(K_{h}\;\times 1.8\times 10^{-5}\;=\;10^{-14}\)

\(K_{h}\;=\;\dfrac{10^{-14}}{1.8\times 10^{-5}}\)

\(\mathbf{K_{h}}\;\mathbf{=\;5.5\times 10^{-10}}\)

Conclusion:

The hydrolysis constant of sodium acetate is \(\mathbf{\;5.5\times 10^{-10}}\).

Concept:

​Basicity of a compound-

• It is the ability of a compound to donate its pair of electrons.

The basicity of a compound depends on the-

• The less electronegative element has greater basicity due to the low attraction of electrons.
• The compound having a negative charge will have a greater ability to donate electrons and higher will be the basicity.
• Compounds with positive charges will not be willing to give up electrons and will be the least basic.
• Molecules, where the electron pair is delocalized by resonance, will be less basic.
• Compounds, where more than one donor centres are present, will be highly basic.

Explanation:

• In decreasing order of basicity is LiCH₃ > LiNH₂ > LiOH > LiF.
• The ions, F⁻, OH⁻, NH₂⁻ and CH₃⁻ are stable ions compared to their conjugate acid.

CONCEPT:

Salt Hydrolysis and pH of Salt Solutions

• Salts are formed by the neutralization of acids and bases. The nature of the parent acid and base determines the pH of the salt solution.
• Based on the strength of the acid and base:
  • Strong acid + strong base → Neutral salt → pH ≈ 7
  • Strong acid + weak base → Acidic salt → pH < 7
  • Weak acid + strong base → Basic salt → pH > 7
• If the salt contains a highly charged metal ion (like Al³⁺), it can hydrolyze water and release H⁺ ions, making the solution acidic.

EXPLANATION:

• Sodium acetate (CH₃COONa):
  • Formed from a strong base (NaOH) and weak acid (acetic acid)
  • Gives a basic solution → pH > 7
• Potassium nitrate (KNO₃):
  • Formed from a strong acid (HNO₃) and strong base (KOH)
  • Neutral salt → pH ≈ 7
• Aluminium chloride (AlCl₃):
  • Formed from a strong acid (HCl) and a weak base (Al(OH)₃)
  • Al³⁺ undergoes hydrolysis to release H⁺ ions → acidic solution
  • pH < 7
• Sodium hydrogen carbonate (NaHCO₃):
  • Amphiprotic salt (can act as acid or base), but overall mildly basic
  • pH slightly > 7

Therefore, the correct answer is Aluminium chloride (Option 3) as it produces a solution with pH < 7.

Correct answer: 2)

Concept:

• The ionic product of water is defined as the product of molar concentrations of H⁺ and OH^- at a specified temperature.
• It is concluded that each aqueous solution whether it is acidic, basic, or neutral possesses both hydrogen H⁺ ion and hydroxyl OH^- ion that are present in the same or different proportions.
• But the ionic product concentration K_w of the water always remains constant 1 × 10^-14 at a temperature of 25°C.

Explanation:

Given,

[H3O+] = 10−6 M

H₂O⇔ H⁺ + OH^-

\(K = \frac{[H^{+}][OH^{-}]}{[H_{2}O]}\)

K x [H₂O] = [H⁺][OH^-]

K_w = [H+][OH-]

[H+]= [OH-] = 10−6 M

So, Kw = [H+][OH-]

Kw= (10−6 ).( 10−6 )

Kw= 10−12 

Conclusion:

Thus, the value of Kw at 90°C temperature is 10−12

Concept:

Indicators:

• They are used to identify the nature of substances.
• They change color when added to acidic or alkaline solutions.
• Natural Indicator:
  •  They are found naturally in the environment 
  • Litmus, red cabbage, turmeric, and china rose
• Artificial Indicators:
  • These are obtained through some chemical reactions.
  • Phenolphthalein, Methyl orange, etc

Explanation:

Summary of Indicators:​

Key Points

Acids:

• They are sour in taste and change the color of blue litmus to red.
• For example, Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3), Acetic acid (CH3COOH), etc.

Bases:

• These are bitter and change the color of the red litmus to blue.
• For example, Sodium hydroxide (NaOH), Calcium hydroxide [Ca(OH)2], potassium hydroxide (KOH), etc.

Correct answer: 2)

Concept:

• The acidic or basic strength of any solution can be described on the basis of pH value.
• pH can be expressed as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution.
• pH can be expressed as, pH=-log[aH+]

• The pKa value is the negative base -10 logarithm of the acid dissociation constant (Ka) of a solution. The higher is the value of pKa the lower will be the acid strength.

• An electron-withdrawing substituent decreases electron density, stabilizes the anion, and thus, increases the acidity of carboxylic acid.

• An electron-releasing substituent increases electron density (negative charge) destabilize the anion and thus, decreases acidity. 
• The effect of substituent, on aromatic acid, in fact, is determined by their inductive and resonance effect.
• Inductive effect affects all positions, i.e., o-, m-, and p-, however, resonance effect affects only o- and p- positions.

Explanation:

• In the case of o-, m-, and p-nitro benzoic acids, the -NO₂ group exerts a greater electron-withdrawing effect when present in the o- and p- positions.
• So, o- and p- nitrobenzoic acids are the strongest acids.
• the smaller the pK_a value, the stronger the acid.
• 

Conclusion:

Thus, the correct decreasing order of acidic strength (i) > (ii) > (iii).

Correct answer: 3)

Concept:

• Phosphoric Acid is a weak acid with the chemical formula H₃PO₄.
• Phosphoric Acid is an acid that contains four atoms of oxygen, one atom of phosphorus, and three atoms of hydrogen.
• H₃PO₃ is called orthophosphorous acid or phosphorous acid. It is one of the phosphorus oxygenic acids.
• Phosphorous acid (H₃PO₃) forms salts known as phosphites.
• Hypophosphorous acid (H₃PO₂), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent.
• Hypophosphoric acid is a mineral acid with the formula H₄P₂O₆, with phosphorus in a formal oxidation state of +4.
• In the solid state, it is present as the dihydrate, H₄P₂O₆·2H₂O.

Explanation:

• The structure of phosphoric acid,(H₃PO₄) has three acidic or ionizable hydrogen.
• H₃PO₃ is an acid with the name phosphorous acid.
• It is a di protonic acid with many applications in many fields.
• It readily undergoes ionization to form two hydrogen ions.

• H₃PO₃ is a diprotic acid. It has two ionizable H atoms.
• While H₃PO₂ is a monobasic acid and has only one ionizable H atom, two H-atoms are directly attached to phosphorus.

• In the case of H₄P₂O₆, it has four ionizable hydrogen atoms.

• Hence, the correct decreasing order of the number of ionizable hydrogen atoms in the following molecules is (iv) > (i) > (ii) > (iii).

Conclusion:

• Thus, the correct decreasing order of the number of ionizable hydrogen atoms in the following molecules is ​ (iv) > (i) > (ii) > (iii).