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101.	Which one of the following is true for any diprotic acid H2X
Answer» Answer: K_a1>K_a2 For any polyprotic acid, first acid constant will always be greater than rest as after losing one proton it becomes difficult to lose another electron and acts as acid.

101.

Which one of the following is true for any diprotic acid H2X

Answer»

Answer: K_a1>K_a2

For any polyprotic acid, first acid constant will always be greater than rest as after losing one proton it becomes difficult to lose another electron and acts as acid.

Discussion

102.	Three reactions involving H2PO4 are given below. (i) H3PO4 + H2O → H3O+ + H2PO-4 (ii) H2PO4 + H2O → HPO24 + H3O+(iii) H2PO4 + OH- → H3PO4 + O2-In which of the above does H2PO-4 act as an acid. (a) (i) only (b) (ii) only (c) (i) & (iii) (d) (iii) only
Answer» (b) (ii) only

Discussion

103.	An acid HA ionises as HA ⇌ H+ + A- The pH of 1.0 M solution is 5. its dissociation constant would be ………(a) 1 x 10-5 (b) 1 x 10-10 (c) 5 (d) 5 x 108
Answer» (b) 1 x 10^-10

Discussion

104.	In [Cr(H2O)6]3+ which one of the following acts as Lewis acid? (a) Cr (b) Cr3+ (c) (HO)6 (d) Cr3+
Answer» Cr³⁺ acts as Lewis acid.

Discussion

105.	Consider the following statements. (i) A Lewis acid is a species that accepts an electron pair. (ii) A Lewis acid is a species that donates an electron pair. (iii) The ligand act as Lewis base. Which of the above statement is / are not correct? (a) (i) only (b) (ii) only (c) (I) & (ii) (d) (ii) & (iii)
Answer» (b) (ii) only

Discussion

106.	H3BO3 accepts hydroxide ion from water as shown below
Answer» H₃BO₃ (aq) + H₂O(l) = B(OH)₄^- + H⁺ Predict the nature of H₃BO₃ using Lewis concept. Boric acid is also called as hydrogen borate or orthoboric acid. It is a weak mono basic Lewis acid of boron and it is written as B(OH)₃ . It accepts hydroxyl (OH^-) ion from water. It does not dissociate to give hydronium (H₃O⁺) ion rather forms metaborate ion and this ions in turn give H₃O ion. B(OH)₃ + H₂O [B(OH)₄]^- + H₃O⁺ Hence it is considered as weak acid.

106.

H3BO3 accepts hydroxide ion from water as shown below

Answer»

H₃BO₃ (aq) + H₂O(l) = B(OH)₄^- + H⁺

Predict the nature of H₃BO₃ using Lewis concept. Boric acid is also called as hydrogen borate or orthoboric acid. It is a weak mono basic Lewis acid of boron and it is written as B(OH)₃ . It accepts hydroxyl (OH^-) ion from water. It does not dissociate to give hydronium (H₃O⁺) ion rather forms metaborate ion and this ions in turn give H₃O ion.

B(OH)₃ + H₂O [B(OH)₄]^- + H₃O⁺ Hence it is considered as weak acid.

Discussion

107.	The concentration of hydroxide ion in a water sample is found to be 2.5 x 10-6 M. Identify the nature of the solution.
Answer» The concentration of OH ion in a water sample is found to be 2.5 x 10 M pOH = – log₁₀ [OH^-] pOH = – 1og₁₀ [2.5 x 10^-6] = – log₁₀ [2.5] – log₁₀ [10^-6] = – 0.3979 – (– 6) = – 0.3979 + 6 pOH = 5.6 We know that, pH + pOH = 14 pH + 5.6 = 14 pH = 14 – 5.6 pH = 8.4 pH = 8.4, shows the nature of the solution is basic.

107.

The concentration of hydroxide ion in a water sample is found to be 2.5 x 10-6 M. Identify the nature of the solution.

Answer»

The concentration of OH ion in a water sample is found to be 2.5 x 10 M

pOH = – log₁₀ [OH^-]

pOH = – 1og₁₀ [2.5 x 10^-6]

= – log₁₀ [2.5] – log₁₀ [10^-6]

= – 0.3979 – (– 6)

= – 0.3979 + 6

pOH = 5.6

We know that,

pH + pOH = 14

pH + 5.6 = 14

pH = 14 – 5.6

pH = 8.4

pH = 8.4, shows the nature of the solution is basic.

Discussion

108.	The concentration of hydrogen ions ¡n a sample of soft drink is 3.8 x 10-3 m. What is the. pH value? Whether the soft drink is acidic (or) basic?
Answer» pH = – log₁₀ [H₃O⁺] = – log₁₀ [3.8 x 10^-3] = – log 3.8 + 3 = 3 – 0.5798 = 2.4202 pH = 2.42 When pH < 7, the soft drink is acidic.

108.

The concentration of hydrogen ions ¡n a sample of soft drink is 3.8 x 10-3 m. What is the. pH value? Whether the soft drink is acidic (or) basic?

Answer»

pH = – log₁₀ [H₃O⁺]

= – log₁₀ [3.8 x 10^-3]

= – log 3.8 + 3

= 3 – 0.5798 = 2.4202

pH = 2.42

When pH < 7, the soft drink is acidic.

Discussion

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Explore topic-wise InterviewSolutions in .

Which one of the following is true for any diprotic acid H2X

Three reactions involving H2PO4 are given below. (i) H3PO4 + H2O → H3O+ + H2PO-4 (ii) H2PO4 + H2O → HPO24 + H3O+(iii) H2PO4 + OH- → H3PO4 + O2-In which of the above does H2PO-4 act as an acid. (a) (i) only (b) (ii) only (c) (i) &amp; (iii) (d) (iii) only

An acid HA ionises as HA ⇌ H+ + A- The pH of 1.0 M solution is 5. its dissociation constant would be ………(a) 1 x 10-5 (b) 1 x 10-10 (c) 5 (d) 5 x 108

In [Cr(H2O)6]3+ which one of the following acts as Lewis acid? (a) Cr (b) Cr3+ (c) (HO)6 (d) Cr3+

H3BO3 accepts hydroxide ion from water as shown below

The concentration of hydroxide ion in a water sample is found to be 2.5 x 10-6 M. Identify the nature of the solution.

The concentration of hydrogen ions ¡n a sample of soft drink is 3.8 x 10-3 m. What is the. pH value? Whether the soft drink is acidic (or) basic?

Three reactions involving H2PO4 are given below. (i) H3PO4 + H2O → H3O+ + H2PO-4 (ii) H2PO4 + H2O → HPO24 + H3O+(iii) H2PO4 + OH- → H3PO4 + O2-In which of the above does H2PO-4 act as an acid. (a) (i) only (b) (ii) only (c) (i) & (iii) (d) (iii) only