Ncert Solutions Chemistry Class 11th

1.39.  (d) Taking reference of the ideal gas equation PV= nRT (Where, P= Pressure, V= volume, n=no of moles, R= gas const, T= temperature). It can thus be concluded that volume is directly proportional to the no. of moles.

1.38 (d) 123.00 has five significant figures. Assertion is wrong statement while reason is a correct statement.

All the compounds are crystalline solids and their solubility in water is guided by both lattice enthalpy and hydration enthalpy. In case of sodium and potassium compounds, the magnitude of lattice enthalpy is quite small as compared of sodium and potassium that are mentioned, readily dissolve in water. However, in case of corresponding magnesium and calcium compounds, the cations have smaller sizes and more magnitude of positive charge. This means that their lattice enthalpies are more as compared to the compounds of sodium and potassium. Therefore, the hydroxides and carbonates of these metals are only sparingly soluble in water.

This is due to the reason that potassium bicarbonate (KHCO₃) formed as an intermediate (when CO₂ gas is passed through ammoniated solution of potassium chloride) is highly soluble in water and cannot be separated by filtration.

(a) Due to its the lowest ionization energy, Cs is considered as the most electropositive element.

(b) Lithium cannot be used in making photoelectric cells because out of all the alkali metals it has the highest ionization energy and thus cannot emit electrons when exposed to light.

(c) Due to small size, lithium does not form alums

Beryllium carbonate is unstable and decomposes to give beryllium oxide and carbon dioxide.

The loosely held s-electron in the outermost valence shell of these elements makes them the most electropositive metals which readily give ions, M+ or M2+.

Li+ has maximum degree of hydration due to its small size and for this reason lithium salts are mostly hydrated.