CBSE Questions for Class 11 Medical Chemistry The S-Block Elements Quiz 8 - MCQExams.com

• LiH is produced by treating lithium metal with hydrogen gas.
  
• It is used for filling meteorological balloons which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde
  

$$Be^{+3}$$ is isoelectronic  with $$Li^{+2}$$. Both the ions are having 1 electron only in their valence shells. So they are isoelectronic with each other.

So the option A is the correct statement for $$Be^{+3}$$.

Hence option A is correct.

• The solubility of a compound depends on the co-relation between lattice enthalpy and hydration enthalpy. If the hydration enthalpy is equal to or greater than the lattice enthalpy, then the salt is water-soluble. More the hydration enthalpy as compared to lattice enthalpy more will be the solubility of salt in water.
• $$MgSO_4$$ is soluble in water but $$BaSO_4$$ is not because of the size of $$Ba^{2+}$$ and $$SO_4^{2-}$$ ions is very large which leads to higher lattice enthalpy than that of hydration enthalpy. Barium hydroxide and barium oxide, are partially soluble in water and Calcium Fluoride is also insoluble due to extremely high lattice energy.

• In all cases, for a particular set of e.g. Group 1 or Group 2 compounds, the thermal stability increases down the group as the ionic radius of the cation increases, and its polarising power decreases.
•   Group 1 compounds tend to be more thermally stable than group 2 compounds because the cation has a smaller charge and a larger ionic radius, and so a lower polarising power. particularly when adjacent metals on the same period are compared. 

It has only one electron in its valence shell and can only take the +1 oxidation state.

Now, in $$KO_2$$, let oxidation number of oxygen be x.

Therefore, $$1+2x=0$$ as $$K=+1$$ and $$KO_2$$ is a neutral molecule.

The oxidation number of oxygen in $$KO_2$$ is $$\cfrac{-1}{2}$$

• Due to diagonal relationship Be and Al exhibit many similar properties but covalency of Be is 4 because it has an absence of d-orbital whereas, covalency of Al is up to 6 due to the presence of vacant d-orbital.
  
• Hence option A is correct answer.
  

$$LiAlH_4$$ is obtained by reacting an excess of $${LiH}$$ with an ethereal solution of $$AlCl_3$$.

$$LiAlH_4$$ is prepared from the reaction between lithium hydride $$(LiH)$$ and aluminium chloride.

$$4LiH + AlCl_3 \rightarrow LiAlH_4 + 3 LiCl$$

So the correct option is B

Similarities of  lithium with magnesium and dissimilarities with that of the other members of the group

Lithium is a very strong element and is equally strong as magnesium.

Li forms $$Li_3N$$ with nitrogen.

It has high melting and boiling points. The boiling point of lithium is $$1330$$ degree centigrade that is comparable to that of magnesium which is $$1100$$ degrees.

Due to small size, the lithium atom has high ionization energy. Hence, it remains inactive to dry air, slowly reactivity with water, liquid bromine and forms a highly stable hydride unlike other alkali metals.