Multiple Choice QuestionsA chemist wishes to prepare a buffer solution of pH = 2.90 that efficiently resists a change in pH yet contains only small concentration of buffering agents which one of the following weak acid along with its salt would be best to use
m-chlorobenzoic acid (pKa = 3.98)
Acetoacetic acid (pKa = 3.58)
2 5-dihydrobenzoic acid (pKa = 2.97)
p-chlorocmanic acid (pKa = 4.41)
C.
2 5-dihydrobenzoic acid (pKa = 2.97)
The buffer solution to be made should effectively resists a change in pH, i.e., should have a higher buffer capacity.
Buffer capacity () =
By one of any two ways, we can obtain it,
(i) The higher the concentration of the components of a buffer mixture, the greater will be the buffer capacity But, the condition is to maintain a small concentrations of buffering components.
(ii) Buffer capacity of a buffer is maximum when the concentration of the weak acid and its salt are equal, i.e. [salt] = [acid].
= pKa + log 1 (as [Salt] = [acid])
pH = pKa = 2.9
As, 2, 5-dihydrobenzoic acid has pKa value = 2.97, hence, it is the best choice for chemist to prepare buffer solution.
NaOH is a strong base. What will the be pH of 5.0 × 10-2 M NaOH solution? (log 2 = 0.3)
14.00
13.70
13.00
12.70
The equilibrium constants of the reactions
and are K1 respectively. The relationship between K1 and K2 will be
K2
K2 = √K1
K1= K2
The value of Kc for the dissociation reaction, H2 (g) 2H (g) is 1.2 × 10-42
This equilibrium mixture contains mainly
H2 (g)
H (g) atom
1.1 M mixture of H2 and H
1.2 M mixture of H2 and H
Among the following, the equilibrium which is not affected by an increase in pressure is
C(s) + H2O (g) CO(g) + H2(g)
3Fe(s) + 4H2O (g) Fe3O4 (s) + 4H2(g)
2SO3(g) 2SO2(g) + O2 (g)
H2 (g) + I2(s) 2Hi(g)
Ksp of CaSO4 is 4 × 10-12. CaSO4 is precipitated on mixing equal volumes of the following solutions.
3 × 10-10 M CaCl2 and 3 × 10-6 M (NH4)2SO4
4 × 10-6 M CaCl2 and 3 × 10-6 M (NH4)2SO4
6 × 10-6 M CaCl2 and 3 × 10-16 M (NH4)2SO4
In all the above cases
What is pH of 2 x 10-8 molar HCl solution? Here, log 2 = 0.301 and log 3 = 0.477.
6.92
9.5
5.4
7.7
Which one of the following species acts as both Bronsted acid and base?
H2PO
HPO
HPO
All of these
The reaction, SO2 + O2 → 2SO2 + Heat.
The equilibrium reaction proceeds in forward direction by
addition of O2
removal of O2
addition of inert gas
cannot proceed
Which is soluble in NaNO3 and dil. HCl mixture and forming salt?
(CH3)3CNH2
(CH3)2CHNH2
(CH3)2NH
(CH3)3N
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