NEET Practice Questions (MCQs) with Answers & Solutions

(C).  ${\mathrm{H}}_2{\mathrm{O}}_2$ is a polar compound and its dipole moment is not zero. It is stable in acid medium

        because its decomposition can be retarded by adding small amounts of acid. It also acts as

        oxidising and reducing agent. Pure ${\mathrm{H}}_2{\mathrm{O}}_2$ is slightly acidic, because its aqueous solution is

        slightly or weakly acidic.

(C).  Sodium hexametaphosphate$-$a polyphosphate, combines with cations $\left(\mathrm{i}.\mathrm{e}., {\mathrm{Ca}}^{2+}, {\mathrm{Mg}}^{2+}\right)$ to

        form soluble complexes.

            $$\begin{gathered} 2{\mathrm{Ca}}^{2+}+{\mathrm{Na}}_2\left[{\mathrm{Na}}_4{\left({\mathrm{PO}}_3\right)}_6\right]\to 4{\mathrm{Na}}^{+}+{\mathrm{Na}}_2\left[{\mathrm{Ca}}_2{\left({\mathrm{PO}}_3\right)}_6\right] \\ \mathrm{complex} \left(\mathrm{soluble}\right) \end{gathered}$$

(A).  Hydrogen form bonds in +1 and –1 oxidation state.

(C).  Washing soda removes both the temporary and permanent hardness by converting soluble

        calcium and magnesium compounds into insoluble carbonates. 

        $$\begin{gathered} {\mathrm{CaCl}}_2+{\mathrm{Na}}_2{\mathrm{CO}}_3\stackrel{ }{\to }{\mathrm{CaCO}}_3+2\mathrm{NaCl} \\ {\mathrm{CaSO}}_4+{\mathrm{Na}}_2{\mathrm{CO}}_3\stackrel{ }{\to }{\mathrm{CaCO}}_3+{\mathrm{Na}}_2{\mathrm{SO}}_4 \\ \mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2+{\mathrm{Na}}_2{\mathrm{CO}}_3\stackrel{ }{\to }{\mathrm{CaCO}}_3+2{\mathrm{NaHCO}}_3 \end{gathered}$$

(A).  The % of para form increases if the temperature is lowered and at absolute zero only para

        form having lowest internal energy exists.

Ordinary dihydrogen is an equilibrium mixture of ortho and para hydrogen.

The amount of ortho and para hydrogen varies with temperature as:

• At 0°K, hydrogen contains mainly para hydrogen which is more stable.
• At the temperature of liquefaction of air, the ratio of ortho and para hydrogen is 1 : 1.
• At the room temperature, the ratio of ortho to para hydrogen is 3 : 1.
• Even at very high temperatures, the ratio of ortho to para hydrogen can never be more than 3 : 1.

Thus, it has been possible to get pure para hydrogen by cooling ordinary hydrogen gas to a very low temperature (close to 20 K) but it is never possible to get a sample of hydrogen containing more than 75% of ortho hydrogen.

(D).   Iron (Fe) does not react with cold water to give ${\mathrm{H}}_2$. However, iron reacts with steam to give ${\mathrm{H}}_2$.

(B).   Hardness of water is due to the presence of bicarbonates, chlorides and sulphates of Ca and

         Mg on it. These ${\mathrm{Ca}}^{2+} \mathrm{and} {\mathrm{Mg}}^{2+}$ ions react with the anions of fatty acids present in soaps to

         form curdy white precipitates. As a result, hard water does not produce lather with soap

         immediately. 

(A).  Because ice is less denser than water.

(B).   Solubility of ionic compounds is less in heavy water.

(A).  ${\mathrm{H}}_2{\mathrm{SO}}_4+{\mathrm{BaO}}_2\stackrel{ }{\to }{\mathrm{BaSO}}_4+{\mathrm{H}}_2{\mathrm{O}}_2$