No, molality of solution does not change with temperature since mass remains unaffected with temperature.

The orbitals which belong to same subshell and same shell are called degenerate orbitals.\({ (3d }_{ xy },{ 3d }_{ { z }^{ 2 } },{ 3d }_{ yz })\) and \(({ 4 \ d }_{ xy },{ 4 \ d }_{ zy },{ 4 \ d }_{ { z }^{ 2 } })\) are the two sets of degenerate orbitals.

In the figure I are of ++ overlap is equal to +- overlap,so net overlap is zero,while in the figure II there is no overlap due to different symmetry.

In CH₄ there are four C-H bonds. The enthalpy of atomisation of 1 mole of CH₄ means dissociation of four moles of C-H bond.
\(\therefore \) C-H bond energy per mol = \(\frac { 1665 \ KJ }{ 4 \ mol } \) = 416.25 KJ mol^-1.

BF3 is an electron deficient compound and hence acts as Lewis acid.NH3 has one lone pair which it can donate to BF₃ and form a coordinate bond. Hence, NH3 acts as lewis base.
\( { H }_{ 3 }{ N }:\rightarrow { BF }_{ 3 } \)

Hydrogen peroxide is decomposed by rough surfaces of glass, alkali oxides present in it and light to form

\({ H }_{ 2 }O \ and \ { O }_{ 2 } \ { 2H }_{ 2 }{ O }_{ 2 }\rightarrow { 2H }_{ 2 }O+{ O }_{ 2 }\)
To prevent this decomposition, \({ H }_{ 2 }{ O }_{ 2 }\)is usually stored in coloured paraffin wax coated plastic or teflon bottles.

2In PbO₂ and SnO₂ , both lead and tin are present in +4 oxidation state, But due to stronger inert pair effect, Pb²⁺ ion is more stable than Sn²⁺ ion. In other words Pb⁴⁺ ions i.e. PbO₂ is more easily reduced to Pb⁺² ions than Sn⁴⁺ ions reduced to Sn²⁺ ions. Thus, PbO₂ acts as a stronger oxidising agent than SnO₂

If a compound decomposes at its boiling point but is steam volatile, water-insoluble and stable at low pressure, steam distillation can be used for its purification. This technique is applied to separate substances which are steam volatile and immiscible with water.

Green house namely carbon dioxide,methane,nitrous oxide(N₂,O),ozone and chloroflurocarbons(CFS's) are reponsible for green house effect,i.e for maintaining temperature of the earth as these absorb the outgoing radiations from the earth's surface