Preparation and Properties of Compounds MCQ Questions & Answers in Inorganic Chemistry | Chemistry

$${K_2}S{O_4}$$  raises the $$bpt.$$  and ensure complete reaction and $$CuS{O_4}$$  acts as catalyst.

Prussian blue $$F{e_4}{\left[ {Fe{{\left( {CN} \right)}_6}} \right]_3}$$   is formed in lassaigne test for nitrogen.
$$3N{a_4}\left[ {Fe{{\left( {CN} \right)}_6}} \right] + 4F{e^{3 + }} \to \mathop {F{e_4}{{\left[ {Fe{{\left( {CN} \right)}_4}} \right]}_6} + 12N{a^ + }}\limits_{{\text{Prussian}}\,{\text{blue}}} $$

$$\eqalign{ & {\text{Normality of}}\,\,3\% \,N{a_2}C{O_3}. \cr & N = \frac{{3 \times 100}}{{53 \times 100}} = 0.566\,N \cr & {\text{For}}\,{H_2}S{O_4}\,{\text{sol}}{\text{.}}\,{N_1} = 0.1,\,{V_1} = 100\,mL \cr & {\text{For}}\,N{a_2}C{O_3}\,sol.\,{N_2} = 0.566.\,{N_2}? \cr & {\text{Now apply}}\,{N_1}{V_1} = {N_2}{V_2} \cr & {V_2} = \frac{{{N_1}{V_1}}}{{{N_2}}} \cr & = \frac{{0.1 \times 100\,mL}}{{0.566}} \cr & = 176.66\,mL \cr} $$

Hence, empirical formula is $$C:H:O = 1:2:1 = C{H_2}O$$

In steam distillation of toluene, the pressure of toluene in vapour is less than pressure of barometer, because it is carried out when a solid or liquid is insoluble in water and is volatile with steam but the impurities are non-volatile.

$$\eqalign{ & \% \,\,{\text{of}}\,\,C = \frac{{12}}{{44}} \times \frac{{0.147}}{{0.2}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 20.045\% \cr & \% \,\,{\text{of}}\,\,H = \frac{2}{{18}} \times \frac{{0.12}}{{0.2}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 6.666\% \cr & \% \,\,{\text{of}}\,\,O = 100 - \left( {20.045 + 6.666} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 73.29\% \cr} $$

Percentage of nitrogen by Kjeldahl’s method
$$\eqalign{ & = \frac{{1.4 \times N \times V}}{{Wt.\,{\text{of organic compound}}}} \cr & = \frac{{1.4 \times 20}}{{0.532}} \times \frac{1}{2} \cr & = 26.32\% \cr} $$

Camphor is used in molecular mass determination due to its volatile nature. The method is called Rast’s camphor method. Camphor acts as a solid solvent which is volatile, hence can be removed easily.

$$\eqalign{ & {\text{Apply the formula }}M.wt \cr & = \frac{{{\text{Acidity}}}}{2}\left( {\frac{{wt\,\,{\text{of}}\,\,Pt\,\,{\text{salt}} \times 195}}{{wt\,\,{\text{of}}\,\,Pt}} - 410} \right) \cr & \therefore \,\,M.wt = \frac{1}{2}\left( {\frac{{0.75 \times 195}}{{0.245}} - 410} \right) \cr & = 93.5 \cr} $$

Kjeldahl’s method is simpler and more convenient than Duma’s method. This method is largely used for the estimation of nitrogen in food stuff, drugs, fertilisers and many other organic compounds. However, this method cannot be used for organic compounds containing nitrogen in the ring such as pyridine, quinoline and organic compounds containing nitro $$\left( { - N{O_2}} \right)$$  and diazo $$\left( { - N = N - } \right)$$   groups.