What is meant by 'demineralised' water and how can it be obtained?
Demineralised water is free from all soluble mineral salts. It does not contain any anions or cations.
Demineralised water is obtained by passing water successively through a cation exchange (in the H+ form) and an anion exchange (in the OH- form) resin.
During the cation exchange process, H+exchanges for Na+, Mg2+, Ca2+, and other cations present in water.
In the anion exchange process, OH- exchanges for anions such as CO2-3, SO2-4 , Cl- , HCO-3 etc. present in water.
OH- ions liberated in reaction (2) neutralize H+ ions liberated in reaction (1), thereby forming water.
H+ (aq) + OH- (aq) → H2O(l)
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
Compare the structures of H2O and H2O2.
Write chemical reactions to show the amphoteric nature of water.
Arrange the following
(i) CaH2, BeH2 and TiH2 in order of increasing electrical conductance.
(ii) LiH, NaH and CsH in order of increasing ionic character.
(iii) H-H, D-D and F-F in order of increasing bond dissociation enthalpy.
(iv) NaH, MgH2 and H2O in order of increasing reducing property.
Discuss the principle and method of softening of hard water by synthetic ion-exchange resins.
What do you understand by the term “non-stoichiometric hydrides”? Do you expect this type of the hydrides to be formed by alkali metals? Justify your answer.
What causes the temporary and permanent hardness of water?
How does H2O2 behave as a bleaching agent?
Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?
Describe the bulk preparation of dihydrogen by electrolytic method. What is the role of an electrolyte in this process?
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.
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?
What is the relationship between the members of following pairs of structures? Are they structural or geometrical isomers or resonance contributors?
(a)
(b)
(c)
List gases which are responsible for greenhouse effect.
Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.
If the speed of light is 3.0 × 108 ms–1, calculate the distance covered by light in 2.00 ns.
Similar to electron diffraction, neutron diffraction microscope is also used for the determination of the structure of molecules. If the wavelength used here is 800 pm, calculate the characteristic velocity associated with the neutron.
Explain the following reactions
(a) Silicon is heated with methyl chloride at high temperature in the presence of copper;
(b) Silicon dioxide is treated with hydrogen fluoride;
(c) CO is heated with ZnO;
(d) Hydrated alumina is treated with aqueous NaOH solution
Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in C2H4 and C2H2 molecules.
If B-Cl bond has a dipole moment, explain why BCl3 molecule has zero dipole moment.
The equilibrium constant expression for a gas reaction is,
Write the balanced chemical equation corresponding to this expression.
A sample of 0.50 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H2SO4. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.