Problem 31 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Match the following items in column I with the corresponding items in column II. Column-I \(\quad\) Column-II (i) \(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}\) (A) Portland cement ingredient (ii) \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\) (B) Castner-Kellner process (iii) \(\mathrm{NaOH}\) (C) Solvay process (iv) \(\mathrm{Ca}_{3} \mathrm{Al}_{2} \mathrm{O}_{6}\) (D) Temporary hardness (a) (i) \(\rightarrow(\mathrm{B})\); (ii) \(\rightarrow(\mathrm{C}) ;\) (iii) \(\rightarrow(\mathrm{A})\); (iv) \(\rightarrow(\mathrm{D})\) (b) (i) \(\rightarrow(\mathrm{C})\); (ii) \(\rightarrow(\mathrm{B})\); (iii) \(\rightarrow\) (D); (iv) \(\rightarrow\) (A) (c) (i) \(\rightarrow(\mathrm{D})\); (ii) \(\rightarrow(\mathrm{A})\); (iii) \(\rightarrow(\mathrm{B})\); (iv) \(\rightarrow(\mathrm{C})\) (d) (i) \(\rightarrow(\mathrm{C})\); (ii) \(\rightarrow\) (D); (iii) \(\rightarrow\) (B); (iv) \(\rightarrow\) (A)

Step-by-Step Solution

Answer

The correct matching is (d) \( (i) \rightarrow (C) \), \( (ii) \rightarrow (D) \), \( (iii) \rightarrow (B) \), \( (iv) \rightarrow (A) \).

Step 1: Match \( \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O} \) with Column II

\( \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O} \) is sodium carbonate decahydrate, commonly known as washing soda. It plays a role in the Solvay process, which is used for the production of sodium carbonate. Hence, it corresponds to (C) Solvay process.

Step 2: Match \( \mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2} \) with Column II

\( \mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2} \) is magnesium bicarbonate. It contributes to temporary hardness in water, as it can be removed by boiling. Therefore, it corresponds to (D) Temporary hardness.

Step 3: Match \( \mathrm{NaOH} \) with Column II

\( \mathrm{NaOH} \) is sodium hydroxide, which is produced by the Castner-Kellner process, also known as the chloralkali process. Hence, it matches with (B) Castner-Kellner process.

Step 4: Match \( \mathrm{Ca}_{3} \mathrm{Al}_{2} \mathrm{O}_{6} \) with Column II

\( \mathrm{Ca}_{3} \mathrm{Al}_{2} \mathrm{O}_{6} \) is tricalcium aluminate, a compound used as an ingredient in Portland cement. Thus, it corresponds to (A) Portland cement ingredient.

Key Concepts

Solvay process

The Solvay process is an industrial method used to produce sodium carbonate, also known as soda ash. This chemical is an essential ingredient in the manufacture of glass, detergents, and other industrial products.
The process involves a series of reactions with sodium chloride, ammonia, and carbon dioxide in water.
Here are some key steps:

• Carbon dioxide is passed into an ammoniated solution of sodium chloride. This forms sodium bicarbonate, which precipitates out.
• The sodium bicarbonate is collected and then heated (calcined) to decompose it into sodium carbonate and carbon dioxide.
• The ammonia is recovered and reused in the process.

The Solvay process is favored because it is efficient and environmentally friendly, recycling nearly all of its reagents.

Temporary hardness

Temporary hardness in water is primarily caused by dissolved bicarbonate minerals such as magnesium bicarbonate (\( \mathrm{Mg(HCO_3)_2} \)) and calcium bicarbonate. This type of hardness can be removed by boiling the water, which converts the bicarbonates into carbonate forms that precipitate out as solids.
When boiled:

• The bicarbonates decompose into carbonates, releasing carbon dioxide and water.
• Example reaction: \( \mathrm{Mg(HCO_3)_2 (aq) \rightarrow MgCO_3 (s) + CO_2 (g) + H_2O (l)} \)
• The carbonate precipitates out, leaving the water softer.

This process is a temporary solution, as the permanent hardness caused by sulfates or chlorides remains unaffected.

Castner-Kellner process

The Castner-Kellner process, also known as the chloralkali process, is utilized for the production of sodium hydroxide (\( \mathrm{NaOH} \)), chlorine gas (\( \mathrm{Cl_2} \)), and hydrogen gas (\( \mathrm{H_2} \)). This method involves the electrolysis of brine, which is a concentrated solution of sodium chloride (salt water).
This is how it works:

• In the electrolytic cell, the sodium ions move to the cathode (negative electrode) where they react with water to produce sodium hydroxide and hydrogen gas.
• At the anode (positive electrode), chlorine ions are oxidized to chlorine gas.
• These two processes are kept apart in the cell to prevent the recombination of produced gases into hypochlorite.

The Castner-Kellner process is critical in industries that need large quantities of caustic soda and chlorine.

Portland cement ingredient

Portland cement is a fundamental building material, and tricalcium aluminate (\( \mathrm{Ca_3Al_2O_6} \)) is one of its key ingredients. The role of tricalcium aluminate in cement is significant as it affects the setting time and hydration characteristics of the cement.
Some characteristics include:

• When mixed with water, tricalcium aluminate reacts quickly, contributing to the initial setting but must be controlled to avoid flash setting.
• It is also responsible for the heat released during the early hydration phases, affecting how the cement behaves in different environmental conditions.
• Additionally, tricalcium aluminate interacts with sulfate ions to form ettringite, which can influence the strength and durability of concrete structures.

Portland cement's properties are carefully regulated by adjusting the proportion of its ingredients, including tricalcium aluminate, to achieve the desired performance in various construction scenarios.