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Advantages of charcoal over wood It has higher calorific value, i.e. higher heat generating efficiency. Charcoal does not produce smoke on burning so it is a clean fuel. It is easier to transport and ready to use in a convenient dry and broken-up form.

(i) It produces large amount of heat energy.

(ii) It is smokeless and pollution free.

(iii) It is easy to store and transport.

Destructive distillation is a process in which a solid is heated in a completely closed container & all it fumes which contains various volatile substances are collected. So destructive distillation of wood does not show any sign of coal. Thus, the answer is option (b).

Two magnetic field lines of force never intersect each other. If the lines intersect, then at the point of intersection there would be two directions (the needle would point towards two directions) for the same magnetic field, which is not possible.

Destructive distillation is a process in which a solid is heated in a completely closed container & all it fumes which contains various volatile substances are collected. So, when destructive distillation of wood is performed & its volatile constituents are studied, 0.25 kg of charcoal was found.

Charcoal is prepared by burning wood in a limited supply of air, so that water and other volatile materials present in it get removed. Charcoal is a better fuel than wood because it has a higher calorific value than wood, and it burns without producing smoke wheras wood produces a lot of smoke on burning. 

(i) The practice of the second village is the best because they are employing a less polluting and less expensive way of fuel generation.
(ii) The first village is promoting no concern for the environment, ignorance and no technological development. The second village is promoting environmental concern, judicious use of resources and sharing.
(iii) Renewable sources of energy like CNG (Compressed Natural Gas) can be used in vehicles, solar energy can be used in place of electricity.

Charcoal is considered a better fuel than wood because:
(i) It has high calorific value.
(ii) It does not produce any smoke.
Disadvantages:
(i) 1 kg of wood on destructive distillation produces only 0.25 kg of charcoal making it an expensive fuel.
(ii) For production of charcoal, more and more trees would have to be cut down which causes deforestation and disturbs the ecological balance of the Earth.

(i) Charcoal can be produced by cutting trees, 1 kg of wood on destructive distillation produces only 0.25 kg of charcoal.

(ii) (a) Charcoal has high calorific value.

(b) Charcoal does not produce any smoke.

(iii) No regard for environment, disregard for health.

(i) [Xe] 4f⁷5d¹6s²

(a) Cr³⁺, half filled t³_2g

(b) Mn³⁺, due to stable d⁵ configuration in Mn²⁺

(c) Ti⁴⁺, No unpaired electrons 

(i) Cu(II) is more stable

Higher is the range lower will be the value of shunt, so milliammeter will be having higher resistance.  

Its atomic number is  26

It is defined as deflection per unit current of Moving coil galvanometer.  

Because it has incompletely filled d orbitals in one of its oxidation state (Cu²⁺).

The value of Bohr magneton :

μ_l = 9.27×10^-27 Am² 

 Due to lanthanoid contract.

The steady decrease in the size of lanthanoid ions (M³⁺) with the increase in atomic number is called lanthanoid contraction. 

Consequences of lanthanoid contraction :

(i) Separation of lanthanoids is difficult due to lanthanoid contraction because due to this contraction their ionic radii is very small.

(ii) The basic strength of hydrofdes decreases from La(OH)₃ to Lu(OH)₃. Due to lanthanoid contraction, the size of M³⁺ ions decreases and there is increase in the covalent character in M - OH bond.

Ce³⁺, ions having the configuration 4f¹5d⁰6d⁰ can easily lose electron to acquire the configuration 4f⁰5d⁰6s⁰ and form Ce⁴⁺ ion.

Electronic configuration of Ce : [Xe] 4f^d 5d¹ 6s². Generally 5d¹ and 6s² electrons are lost by the lanthanoids in their reactions i.e., they exhibit +3 oxidation states. But Ce exhibit + 4 oxidation state also because it gains extra stability by losing 4f¹ electron because it will give rise to completely filled orbitals.

(iii) both have similar atomic radius. 

It is because after losing one more electron Ce acquires stable 4f⁰ electronic configuration.

As the size decreases from La to Lu, stability of oxosalts also decreases.

Zr, a member of 4d series and Hf, a member of 5d series, belong to same group. They are chemically quite similar yet their separation is difficult. The reason is that both have same size due to lanthanoid contraction. The radii of these elements are 160 pm (h) and 159 pm (Hf).

Actinoids exhibit a large number of oxidation states because 5f ,6d and 7s levels have almost comparable energies (very small energy difference between sub-shells than the energy difference between 4f and 5d orbitals in case of Lanthanoids.

KMnO4 acts as an oxidising agent in alkaline medium. When alkaline KMnO4 is treated with KI, iodide ion is oxidised to  IO₃^–

(ii) Both assertion and reason are true but reason is not the correct explanation of assertion.

(i) Both assertion and reason are true, and reason is the correct explanation of the assertion.

(1) True 

(2) False. On addition of universal indicator the colour of table salt changes to green.

(3) False. Borax is Na₂B₄O₇.9H₂O 

(4) False. Boron – 10 is used in treatment of brain tumour. 

(5) True

(i) Vanadium (V) oxide in contact process for oxidation of SO₂ to SO₃.

(ii) Finely divided iron in Haber’s process in conversion of N₂ and H₂ to NH₃.

(iii) MnO₂ in preparation of oxygen from KClO₃.

Mendeleev's classification is superior to the earlier classifications: 

(i) Mendeleev's developed a periodic table of elements wherein the elements were arranged on the basis of their atomic mass and also on the similarity in chemical properties. 

(ii) Among chemical properties, he took the formulae of the hydrides and oxides formed by an element as one of the basic properties of an element for classification.

1. In the above process charging is by:

• Friction

2. Carpet is found to be positive body which means that electrons are lost from carpet to rubber shoe. Hence rubber shoe acquires charge and mass.

(i) Conservative

Inside a spherical shell electrical field is zero. This is called electrostatic shielding. Hence it is safe to be inside a vehicle rather than outside.

1. Normally outwards from the surface.

Total flux = \(\frac{40\times10^{-3}}{8.85\times10^{-12}}\) = 4.51 x 10⁹Nm²C^-1

2. Through one face = \(\frac{4.51\times10^9}{6}\) = 0.75 x 10⁹Nm²C^-1

3. Electric flux decreases because flux depends on permittivity of medium.