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
(i) 0.003MHCl:
H2O + HCl ↔ H3O+ + Cl-
Since HCl is completely ionized,
[H3O+] = [ HCl]
⇒ [H3O+] = = 0.003
Now
pH = -log [H3O+] = -log (0.003)
= 2.52
Hence, the pH of the solution is 2.52.
(b) 0.005 M NaOH
NaOH(aq) ↔ Na+(aq) + HO-(aq)
[NaOH] = [ HO-]
⇒ [ HO-] = 0.05
pOH = -log[ HO-] = -log (0.05)
= 2.30
∴ pH = 14 - 2.30 = 11.70
Hence, the pH of the solution is 11.70.
(c) 0.002 M HBr
HBr + H2O ↔ H3O+ + Br-
[HBr] = [H3O+]
⇒ [H3O+] = 0.002
∴ pH = -log [H3O+] = -log (0.002)
= 2.69
Hence, the pH of the solution is 2.69.
(d) 0.002 M KOH
KOH(aq) ↔ K+(aq) + OH-(aq)
[OH-] = [KOH]
⇒ [OH-] = 0.002
Now pOH = -log[OH-] = -log (0.002)
= 2.69
∴ pH = 14-2.69 = 11.31
Hence, the pH of the solution is 11.31.
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?
The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.
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.
Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:
CH4 (g) + H2O (g) ↔ CO (g) + 3H2 (g)
(a) Write as expression for Kp for the above reaction.
(b) How will the values of Kp and composition of equilibrium mixture be affected by
(i) increasing the pressure
(ii) increasing the temperature
(iii) using a catalyst ?
At 700 K, equilibrium constant for the reaction:
H2 (g) + I2 (g) ↔ 2HI (g)
is 54.8. If 0.5 mol L–1 of HI(g) is present at equilibrium at 700 K, what are the concentration of H2(g) and I2(g) assuming that we initially started with HI(g) and allowed it to reach equilibrium at 700K?
At 473 K, equilibrium constant Kc for decomposition of phosphorus pentachloride, PCl5 is 8.3 ×10-3. If decomposition is depicted as,
PCl5 (g) ↔ PCl3 (g) + Cl2 (g) ΔrH0 = 124.0 kJ mol–1
(a) write an expression for Kc for the reaction.
(b) what is the value of Kc for the reverse reaction at the same temperature ?
(c) what would be the effect on Kc if (i) more PCl5 is added (ii) pressure is increased (iii) the temperature is increased ?
Find out the value of Kc for each of the following equilibria from the value of Kp:
(i) 2NOCl (g) ↔ 2NO (g) + Cl2 (g); Kp = 1.8 × 10–2 at 500 K
(ii) CaCO3 (s) ↔ CaO(s) + CO2(g); Kp = 167 at 1073 K
Ionic product of water at 310 K is 2.7 x 10-14. What is the pH of neutral water at this temperature?
Reaction between N2 and O2– takes place as follows:
2N2 (g) + O2 (g) ↔ 2N2O (g)
If a mixture of 0.482 mol N2 and 0.933 mol of O2 is placed in a 10 L reaction vessel and allowed to form N2O at a temperature for which Kc = 2.0 × 10–37, determine the composition of equilibrium mixture.
Write the expression for the equilibrium constant, Kc for each of the following reactions:
(i) 2NOCl (g) ↔ 2NO (g) + Cl2 (g)
(ii) 2Cu(NO3)2 (s) ↔ 2CuO (s) + 4NO2 (g) + O2 (g)
(iii) CH3COOC2H5(aq) + H2O(l) ↔ CH3COOH (aq) + C2H5OH (aq)
(iv) Fe3+ (aq) + 3OH– (aq) ↔ Fe(OH)3 (s)
(v) I2 (s) + 5F2 ↔ 2IF5
How do you account for the formation of ethane during chlorination of methane?
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
What are the common physical and chemical features of alkali metals?
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4
Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
What is the basic theme of organisation in the periodic table?
Explain the formation of a chemical bond.
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
The enthalpies of all elements in their standard states are:
(i) unity
(ii) zero
(iii) < 0
(iv) different for each element
For the following bond cleavages, use curved-arrows to show the electron flow and classify each as homolysis or heterolysis. Identify reactive intermediate produced as free radical, carbocation and carbanion.
Use the periodic table to answer the following questions.
(a) Identify an element with five electrons in the outer subshell.
(b) Identify an element that would tend to lose two electrons.
(c) Identify an element that would tend to gain two electrons.
(d) Identify the group having metal, non-metal, liquid as well as gas at the room temperature.
Is there any change in the hybridisation of B and N atoms as a result of the following reaction?
BF3 + NH3 → F3B.NH3
Write the names of isotopes of hydrogen. What is the mass ratio of these isotopes?
Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below:
1Pa = 1N m–2
If mass of air at sea level is 1034 g cm–2, calculate the pressure in Pascal.
Why is Wurtz reaction not preferred for the preparation of alkanes containing odd number of carbon atoms? Illustrate your answer by taking one example.
Identify the functional groups in the following compounds
What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?
What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He+ spectrum?