pH of a solution of a strong acid is 5.0. What will be the pH of the solution obtained after diluting the given solution a 100 times?
pH = 5 i.e., [H+] = 10-5 mol L-1
On dilution by 100 times [H+] = 10-7 mol L-1 For a very dilute solution,
Total [H+] = [H30+ ions from acid] + [H20+ ions from water]
= 10–7 + 10–7
pH = -log[H+] = -log (2 x 10-7) = 7 – log 2
= 7-0.3010 = 6.6990
Arrange the following in increasing order of pH.
KN03(aq), CH3COONa(aq), NH4Cl(aq), C6H5COONH4(aq)
For the equilibrium 2 NOCl(g)——-> 2NO(g) + Cl2(g) the value of the equilibrium constant Kc is 3.75 x 10-6 at 1069 K. Calculate the Kp for the reaction at this temperature?
The equilibrium constant expression for a gas reaction is,
Write the balanced chemical equation corresponding to this expression.
Classify the following species into Lewis acids and Lewis bases and show how these can act as Lewis acid/Lewis base?
(a) OH– ions (b) F– (c) H+ (d) BCl3
A sparingly soluble salt gets precipitated only when the product of concentration of its ions in the solution (Qsp) becomes greater than its solubility product. If the solubility of BaS04 in water is 8 x 10-4 mol dm-3, calculate its solubility in 0.01 mol dm-3 of H2S04.
The species H20, HCO3–, HSO4– and NH3 can act both as Bronsted acid and base. For each case, give the corresponding conjugate acid and base.
Ionization constant of a weak base MOH, is given by the expression
Values of ionization constant of some weak bases at a particular temperature are given below:
| Base | Dimethylamine | Urea | Pyridine | Ammonia |
| 5.4 x 10-4 | 1.3 x 10-14 | 1.77 x lO-9 | 1.77 xlO-5 |
Arrange the bases in decreasing order of the extent of their ionization at equilibrium. Which of the above base is the strongest?
A reaction between ammonia and boron trifluoride is given below:
:NH3 + BF3 →H3N : BF3
Identify the acid and base in this reaction. Which theory explains it? What is the hybridization of B and N in the reactants?
The ionization of hydrochloric acid in water is given below:
HCl(aq) + H20(l) ⇌H30 + (aq) +Cl–(aq)
Label two conjugate acid-base pairs in this ionization.
The value of Kc for the reaction
2HI(g) ⇌H2(g) + I2(g) is 1 x 10-4. At a given time, the composition of reaction mixture is [HI] = 2 x 10-5 mol, [H2] = 1 x 10-5 mol and [I2] = 1 x 10-5 mol. In which direction will the reaction proceed?
Explain why pure liquids and solids can be ignored while writing the value of equilibrium constants.
Predict which of the following will have appreciable concentration of reactants and products:
The degree of ionization of a 0.1 M bromoacetic acid solution is 0.132. Calculate the pH of the solution and the PKa of bromoacetic acid.
Calculate the volume of water required to dissolve 0.1 g lead (II) chloride to get a saturated solution. (Ksp of PbCl2 = 3.2 x 10-8, atomic mass of Pb = 207 u).
A mixture of 1.57 mol of N2, 1.92 mol of H2 and 8.13 mol of NH3is introduced into a 20 L reaction vessel at 500 K. At this temperature, the equilibrium constant Kc for the reaction
Is this reaction at equilibrium? If not, what is the direction of net reaction?
Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure bp increasing the volume?
The ionization constant of HF, HCOOH and HCN at 298 K are is 6.8 x 10-4 , 1.8 x 10-4 and 4.8 x 10-9 respectively, Calculate the ionization constant of the corresponding conjugate base.
Given the equilibrium N2O4 (g) ——->2NO2 (g) K=0.15 atm at 298 K
(a) What is Kp using pressure in torr?
(b) What is Kc using units of moles per litre.
A liquid is in equilibrium with its vapours in a sealed container at a fixed temperature. The volume of the container is suddenly increased, (i) What is the initial effect of the change on the vapour pressure? (ii) How do the rates of evaporation and condensation change initially? (iii) What happens when equilibrium is restored finally and what will be the final vapour pressure?
For the following equilibrium, K =6.3 x 1014 at 1000 K. NO(g)+O3 —–>NO2(g) + O2(g) Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is Kc for the reverse reaction ?
K =0.04 atm at 898 K for the equilibrium shown below. What is the equilibrium concentration ok C2H6 when it is placed in a flask at 4 atm pressure,and allowed to come to equilibrium.
One of the reactions that takes place in producing steel from iron ore is the reduction of iron
(II) oxide by carbon monoxide to give iron metal and C02
FeO(s) + CO(g) ———>Fe(s) + C02(g) ; Kp = 0.265 atm at 1050 K
What are the equilibrium partial pressures of CO and C02 at 1050 K if the initial pressures are: PCO = 1.4 atm and PCO2 = 0.80 atm?
What is the effect of:
(i) addition of H2 (ii) addition of CH3OH
(iii) removal of CO (iv) removal of CH3OH
The concentration of hydrogen ions in a sample of soft drink is 3.8 x 10-3 M. What is the pH value?
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 ions in the solution and its pH.
Assuming complete dissociation, calculate the pH of the following solutions:
(a) 0.003 M HCl (b) 0.005 M NaOH (c) 0.002 M HBr (d) 0.002 M KOH
In the reaction A + B———> C + D, what will happen to the equilibrium if concentration of A is increased?
(b) The equilibrium constant for a reaction is 2 x 10-23 at 25 °C and 2 x 10-2 at 50 °C. Is the reaction endothermic or exothermic?
(c) Mention at least three ways by which the concentration of S03 can be increased in the following reaction in a state of equilibrium.
Ka for CH3COOH is 1.8 x 10-5 and Kb for NH4OH is 1.8 x 10-5. The pH of ammonium acetate will be
(a) 7.005
(b) 4.75
(c) 7.0
(d) Between 6 and 7
For the reaction N204(g) ⇌2N02(g), the value of K is 50 at 400 K and 1700 at 500 K. Which of the following options is correct?
(a) The reaction is endothermic.
(b) The reaction is exothermic.
(c) If NO2(g) and N204(g) are mixed 400 K at partial pressures 20 bar and 2 bar respectively, more N204(g) will be formed.
(d) The entropy of the system increases.
pH of a solution of a strong acid is 5.0. What will be the pH of the solution obtained after diluting the given solution a 100 times?
Calculate the pH of a solution formed by mixing equal volumes of two solutions A and B of a strong acid having pH = 6 and pH = 4 respectively.
