For the following equilibrium, N2O4 2NO2 in the gaseous phase, NO2 is 50% of the total volume when equilibrium is set up. Hence, per cent of dissociation of N2O4 is
50%
25%
66.66%
33.33%
1 mL of 0.01 N HCl is added to 999 mL solution of 0.1 N Na2SO4. The pH of the resulting solution will
2
7
5
1
The equilibrium constants for the reaction,
Br2 2Br → 1
at 500 K and 700 K are 1 × 10-10 and 1 × 10-5 respectively. The reaction is
endothermic
exothermic
fast
slow
A 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