Question

The INCORRECT statement is :

• A. Lithium is least reactive with water among the alkali metals.
• B. $LiCl$ crystallises from aqueous solution as $\ce{LiCl.2H2O.}$
• C. Lithium is the strongest reducing agent among the alkali metals.
• D. $\ce{LiNO3}$ decomposes on heating to give $\ce{LiNO2}$ and $\ce{O2}$.

Answer 1

The Correct Option is D

To determine the incorrect statement from the given options, let's examine each one in the context of common chemical knowledge about lithium and alkali metals.

1. Lithium is least reactive with water among the alkali metals.
   • This statement is true. Among the alkali metals, lithium is indeed the least reactive with water. This is due to its higher ionization energy and smaller atomic size compared to other alkali metals like sodium and potassium.
2. $LiCl$ crystallises from aqueous solution as $\ce{LiCl.2H2O}$.
   • This statement is true. Lithium chloride, when crystallized from aqueous solution, forms a dihydrate compound $\ce{LiCl.2H2O}$.
3. Lithium is the strongest reducing agent among the alkali metals.
   • This statement is true. Lithium, despite being the least reactive in terms of atom-to-atom comparisons like reactivity with water, is the strongest reducing agent due to its high negative electrode potential.
4. $\ce{LiNO3}$ decomposes on heating to give $\ce{LiNO2}$ and $\ce{O2}$.
   • This statement is incorrect. Lithium nitrate decomposes upon heating to form lithium oxide $\ce{Li2O}$, nitrogen dioxide $\ce{NO2}$, and oxygen $\ce{O2}$. The correct decomposition reaction is: $$4\ce{LiNO3} \rightarrow 2\ce{Li2O} + 4\ce{NO2} + \ce{O2}$$

Therefore, the incorrect statement is that $\ce{LiNO3}$ decomposes on heating to give $\ce{LiNO2}$ and $\ce{O2}$.