Ncert Solutions Chemistry Class 11th
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7.46. The ionization constant of acetic acid is 1.74 x 10-5. Calculate the degree of dissociation of acetic acid in its 0.05 M solution. Calculate the concentration of acetate ion in the solution and its pH.
7.46. The ionization constant of acetic acid is 1.74 x 10-5. Calculate the degree of dissociation of acetic acid in its 0.05 M solution. Calculate the concentration of acetate ion in the solution and its pH.
The dissociation equilibrium is
CH3? COOH? CH3? COO− + H+.
Let α be the degree of dissociation.
The equilibrium concentrations of CH3? COOH, CH3COO− and H+ are c (1−α), c (α) and c (α) respectively.
The equilibrium constant expression is Kc? =
Upvote 
7.45. The-first ionization constant of H2S is 9.1 x 10-8. Calculate the concentration of HS– ions in its 0.1 M solution and how will this concentration be affected if the solution is 0.1 M in HCl also? If the second dissociation constant of H2S is 1.2 x 10--13, calculate the concentration of S2-under both conditions.
7.45. The-first ionization constant of H2S is 9.1 x 10-8. Calculate the concentration of HS– ions in its 0.1 M solution and how will this concentration be affected if the solution is 0.1 M in HCl also? If the second dissociation constant of H2S is 1.2 x 10--13, calculate the concentration of S2-under both conditions.
(i) To calculate [HS−] in absence of HCl:
Let, [HS−] = x M.
H2? S? H+ + HS−
The initial concentrations of H2? S, H+ and HS− are 0.1 M, 0 M and 0 M respectively.
Their final concentrations are 0.1-x M, x M and x M respectively.
Ka? = [H2? S] [H+] [HS−]?
9.1×
Upvote 7.44. The ionization constant of phenol is 1.0 x 10-10. What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01 M in sodium phenolate?
7.44. The ionization constant of phenol is 1.0 x 10-10. What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01 M in sodium phenolate?
C6H5OH? C6H5O- + H+
| C6H5OH | C6H5O- | H+ |
Initial | 0.05 M | 0 | 0 |
After dissociation | 0.05 –x | x | x |
Ka = x2 / (0.05 - x) = 1.0 x 10-10
=> x2 / 0.05 = 1.0 x 10-10
=> x2 = 5 x 10-12
=> x= 2.2 x 10-6 M
In presence of 0.01 C6H5Na, suppose y is the am
Upvote 7.43. The ionization constant of HF, HCOOH and HCN at 298 K are is 6.8 x 10-4, 1.8x 10-4 and 4.8 x 10-9 respectively, calculate the ionization constant of the corresponding conjugate base.
7.43. The ionization constant of HF, HCOOH and HCN at 298 K are is 6.8 x 10-4, 1.8x 10-4 and 4.8 x 10-9 respectively, calculate the ionization constant of the corresponding conjugate base.
For F–, Kb =Kw/Ka= 10-14/ (6.8 x 10-4)
= 1.47 x 10-11 = 1.5 x 10-11 .
For HCOO-, Kb = 10-14/ (1.8 x 10-4)
= 5.6 x 10-11
For CN–, Kb= 10-14/ (4.8 X 10-9)
= 2.08 x 10-6
Upvote 7.42. The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.
7.42. The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.
pH = – log [H+] or log [H+] = – pH = – 3.76 = 4.24
Therefore, [H+] = Antilog 4.24 = 1.738 x 10-4 = 1.74 x 10-4 M
Upvote 7.41. The concentration of hydrogen ions in a sample of soft drink is 3.8 x 10-3 M. What is the pH value?
7.41. The concentration of hydrogen ions in a sample of soft drink is 3.8 x 10-3 M. What is the pH value?
pH = – log [H+] = – log (3.8 x 10-3) = – log 3.8 + 3 = 3 – 0.5798 = 2.4202 = 2.42
Upvote 7.40. Classify the following species into Lewis acids and Lewis bases and show how these can act as Lewis acid/Lewis base?
(a) OH– (b) F– (c) H+ (d) BCl3
7.40. Classify the following species into Lewis acids and Lewis bases and show how these can act as Lewis acid/Lewis base?
(a) OH– (b) F– (c) H+ (d) BCl3
(a) OH– ions can donate an electron pair and act as Lewis base.
(b) F– ions can donate an electron pair and actas Lewis base.
(c) H+ ions can accept an electron pair and act as Lewis acid.
(d) BCl3 can accept an electron pair since Boron atom is electron deficient. It
Upvote <p><strong>7.39. The species H<sub>2</sub>O, HCO<sub>3</sub><sup>–</sup>, HSO<sub>4</sub><sup>–</sup> and NH<sub>3</sub> can act both as Bronsted acid and base. For each case, give the corresponding conjugate acid and base. </strong></p>
7.38. Write the conjugate acids for the following Bronsted bases:
NH2, NH3 and HCOO–
7.38. Write the conjugate acids for the following Bronsted bases:
NH2, NH3 and HCOO–
7.37. What will be the conjugate bases for the Bronsted acids: HF, H2SO4 and H2CO3?
7.37. What will be the conjugate bases for the Bronsted acids: HF, H2SO4 and H2CO3?