sblock Elements 2 Question 8
8. Match the following items in Column I with the corresponding items in Column II.
(2019 Main, 11 Jan II)
$$ \begin{array}{|c|c|c|c|} \hline & \text { Column I } & & \text { Column II } \\ \hline \text { (i) } & \mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O} & \text { A. } & \begin{array}{l} \text { Portland cement } \\ \text { ingredient } \end{array} \\ \hline \text { (ii) } & \mathrm{Mg}\left(\mathrm{HCO}_3\right)_2 & \text { B. } & \text { Castner-Kellner process } \\ \hline \text { (iii) } & \mathrm{NaOH} & \text { C. } & \text { Solvay process } \\ \hline \text { (iv) } & \mathrm{Ca}_3 \mathrm{Al}_2 \mathrm{O}_6 & \text { D. } & \text { Temporary hardness } \\ \hline \end{array} $$
(a) (i) - (D); (ii) - (A); (iii) - (B); (iv) - (C)
(b) (i) - (B); (ii) - (C); (iii) - (A); (iv) - (D)
(c) (i) - (C); (ii) - (B); (iii) - (D); (iv) - (A)
(d) (i) - (C); (ii) - (D); (iii) - (B); (iv) - (A)
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Answer:
Correct Answer: 8. (d)
Solution: (i) Washing soda $\left(\mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O}\right)$ is manufactured in Solvay process. In this method, $\mathrm{CO}_2$ gas is passed through a conc. solution of NaCl saturated with $\mathrm{NH}_3$. It gives ammonium carbonate followed by ammonium hydrogen carbonate.
The obtained $\mathrm{NH}_4 \mathrm{HCO}_3$ is treated with solution of NaCl which result in the formation of $\mathrm{NaHCO}_3$. The crystal obtained are heated to obtain $\mathrm{Na}_2 \mathrm{CO}_3$.
$\begin{gathered}\mathrm{NaCl}+\mathrm{NH}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{NaHCO}_3+\mathrm{NH}_4 \mathrm{Cl} \\ 2 \mathrm{NaHCO}_3 \xrightarrow[-\mathrm{H}_2 \mathrm{O}, \mathrm{CO}_2]{\Delta} \mathrm{Na}_2 \mathrm{CO}_3 \xrightarrow{\text { Crystallisation }} \mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O}\end{gathered}$
(ii) $\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2$ and $\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$ cause temporary hardness to water that can be easily removed by boiling.
(iii) NaOH is manufactured by Castner-Kellner process. In this reaction, Na amalgam flows out and treated with water to give NaOH and $\mathrm{H}_2$ gas. During electrolysis,hydrogen is evolved at cathode and chlorine is evolved at anode, which are the by product of this process.
(iv) Portland cement constitutes, tricalcium aluminosilicate, $3 \mathrm{CaO} \cdot \mathrm{Al}_2 \mathrm{O}_3 \cdot \mathrm{SiO}_2$,
i.e. $\mathrm{Ca}_3 \mathrm{Al}_2 \mathrm{O}_6 \cdot \mathrm{SiO}_2$.
BETA
