Chemistry MCQs for NEET — Practice Questions with Answers

(A). In air, a layer of $N{a}_{2}O$, NaOH and $N{a}_{2}C{O}_3$ is formed on its surface which loses its lustre.

      $4Na+O_2\to 2N{a}_{2}O\stackrel{2H_{2}O}{\to }4NaOH\stackrel{2C{O}_2}{\to }2N{a}_{2}C{O}_3+2H_{2}O$

(C) $N{a}_{2}O+H_{2}O\to 2NaOH$

     $2N{a}_{2}O\stackrel{400°C}{\to }N{a}_2{O}_2+2Na$

(C). The hydration energy of the ions of alkaline earth metals ($M^{2+}$) is nearly 4 or 5 times greater than that of alkali metals because of their small size and increased charge.

(A). Ionic radius increases as the atomic number of alkali metal increases.

(B). Because of small size, they are more closely packed in the crystal lattice. So they have comparatively stronger metallic bonds and so more denser and harder than alkali metals.

(A). The ionisation potential value of Lithium is maximum among alkali metals i.e. its tendency to ionise to give $L{i}^{+}$ ions should be the minimum i.e. Li should be the poorest reducing agent. But, lithium is the strongest reducing agent in aq. solution. This is due to the largest value of hydration energy of $L{i}^{+}$ ions.

(C). Due to greater polarisation by $L{i}^{+}$ ion, LiCl acquires some covalent character. Thus the ionisation of LiCl will be less than that of NaCl in water.

(A). $BeC{l}_2$ is hygroscopic and fumes in air due to hydrolysis. It is also covalent in nature due to small size and relatively high charge on $B{e}^{2+}$ ion. Due to small size electrons in Be are tightly held by nuclear forces and they are not excited to higher energy levels. Thus Be does not give flame colouration.

(D). The divalent $C{a}^{2+}$ ion has no unpaired electron, hence, its compounds are diamagnetic and colourless, provided their anions are also colourless.

(C). $Ca+H_2\to Ca{H}_2$