NEET Practice Questions (MCQs) with Answers & Solutions

(a) Elements having reduction potential of -0.41V or below can liberate hydrogen from cold water. Such as alkali metals Ba, Sr and Ca.

Also Zn-Cu and Al-Hg couples liberate hydrogen with cold water.

1.5 N means 1.5 g eq wt in 1 L solution.

N= weight/eq.wt (eq wt for hydrogen peroxide = 17 g)

Therefore, 1.5 = wt/17 or wt = 1.5 X17 = 25.5 g

Now, from the equation we know that 68 g of H2O2 gives 22.4 L of Oxygen.

Therefore, 25.5 g of Hydrogen peroxide gives- 22.4 X25.5/68 = 8.4 L

(b) I group (alkali metals) II group (alkaline earth metals except Be, Mg) forms ionic hydrides.

(c) Hydrogen of high purity is obtained by electrolysing aqueous barium hydroxide in presence of Ni electrodes.

             $$\begin{gathered} 2e + 2{\mathrm{H}}_3{\mathrm{O}}^{+}\stackrel{ }{\to }2{\mathrm{H}}_2\mathrm{O} + \frac{1}{2}{\mathrm{H}}_2 \\ 2{\mathrm{OH}}^{-}\stackrel{ }{\to }{\mathrm{H}}_2\mathrm{O} + \frac{1}{2}{\mathrm{O}}_2 + 2e \\ \mathrm{Also} \mathrm{pure} \mathrm{metal} \mathrm{hydrides} \mathrm{give} \mathrm{pure} {\mathrm{H}}_2 \\ \mathrm{NaH} + {\mathrm{H}}_2\mathrm{O} \stackrel{ }{\to }\mathrm{NaOH} + {\mathrm{H}}_2 \end{gathered}$$

a.

Ortho form is more stable than para form at and above room temperature, whereas at low temperature para form is more stable.

(a) Hydrogen reacts with active metals(Like alkali and alkaline earth metals) form corresponding hydrides.

                 $\mathrm{Ca}\left(\mathrm{s}\right) + {\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{ }{\to }{\mathrm{CaH}}_2$

(a) 

 decomposition can be speed up by increasing the temperature, which triggers the reaction of thermal decomposition. This reaction can be carried out in a liquid or vapour phase.

Usually the rate of reaction is increased by adding catalysts to the reactor. Almost all types of catalyst can be used with this reaction:

heterogeneous (e.g. silver, gold, iron),

homogeneous (iodide or iron ions) and enzymes (catalase).

This reaction is exothermic. It produces large amount of heat (ΔH=-2884.5 kJ/kg H2O2 for pure compound),

which further increases rate of reaction and makes reaction self-sustaining after phase of catalytic initiation. Thermal decomposition is a very complex reaction,

In many industries decomposition of hydrogen peroxide is used e.g.to produce sodium perborate and sodium percarbonate (bleaching agents in solid and liquid detergents). In textile industry hydrogen peroxide bleach and deodorize textiles, wood pulp, hair, fur, etc

(b) $\mathrm{NaH} + {\mathrm{H}}_2\mathrm{O} \stackrel{ }{\to }\mathrm{NaOH} + {\mathrm{H}}_2$