Problem 11 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Identify the incorrect statement regarding heavy water : [Main Online April 9, 2016] (a) It reacts with \(\mathrm{SO}_{3}\) to form deuterated sulphuric acid \(\left(\mathrm{D}_{2} \mathrm{SO}_{4}\right)\). (b) It is used as a coolant in nuclear reactors. (c) It reacts with \(\mathrm{CaC}_{2}\) to produce \(\mathrm{C}_{2} \mathrm{D}_{2}\) and \(\mathrm{Ca}(\mathrm{OD})_{2}\). (d) It reacts with \(\mathrm{Al}_{4} \mathrm{C}_{3}\) to produce \(\mathrm{CD}_{4}\) and \(\mathrm{Al}(\mathrm{OD})_{3}\).

Step-by-Step Solution

Answer

All statements are correct based on standard deuterium chemistry.

Step 1: Understand Heavy Water and Its Reactions

Heavy water, denoted as D₂O, is chemically similar to ordinary water but with the hydrogen atoms replaced by deuterium, a heavier isotope of hydrogen. It can undergo chemical reactions similar to those of water but incorporates deuterium instead of hydrogen, resulting in deuterated products.

Step 2: Evaluate Each Statement

We need to examine each of the given statements regarding the reaction of heavy water (D₂O) and determine if they are chemically valid.

Step 3: Statement (a) Evaluation: Reaction with SO₃

The reaction of heavy water with SO₃ to form deuterated sulfuric acid (D₂SO₄) is chemically plausible. This is analogous to H₂O reacting with SO₃ to form H₂SO₄. Thus, statement (a) is correct.

Step 4: Statement (b) Evaluation: Use as Coolant

Heavy water is indeed used as a coolant and a moderator in nuclear reactors due to its ability to slow down neutrons efficiently. Hence, statement (b) is correct.

Step 5: Statement (c) Evaluation: Reaction with CaC₂

CaC₂ (calcium carbide) reacts with water to produce acetylene (C₂H₂) and calcium hydroxide. Similarly, heavy water would react to form deuterated acetylene (C₂D₂) and calcium deuteroxide (Ca(OD)₂). Therefore, statement (c) is correct.

Step 6: Statement (d) Evaluation: Reaction with Al₄C₃

Al₄C₃ (aluminum carbide) reacts with water to produce methane (CH₄) and aluminum hydroxide. When reacted with heavy water, it should produce CD₄ and Al(OD)₃. The statement claims it produces CD₄, which is correct. However, Al(OD)₃ is also a valid product; thus, statement (d) is actually correct.

Step 7: Identify the Incorrect Statement

Assessing all reactions, all statements appear chemically correct based on heavy water reactions, implying there might be a misunderstanding or error in the question unless there's context not considered.

Key Concepts

Deuterium Reactions

Heavy water, known as D₂O, is a form of water where hydrogen atoms are replaced by deuterium, a stable isotope of hydrogen that is twice as heavy. This substitution leads to slightly different chemical behavior in reactions when compared to normal water. The deuterium in heavy water can engage in typical water-like reactions, but the products formed are termed 'deuterated compounds'.

Important points about deuterium reactions include:

• They follow similar pathways as ordinary hydrogen due to deuterium's chemical similarity to hydrogen.
• The resulting products like deuterated acids and other compounds are used in scientific research to trace reactions and understand mechanisms.
• The slight variations in reaction kinetics due to the increased mass of deuterium compared to ordinary hydrogen sometimes lead to different reaction rates.

Understanding these reactions is important in fields such as synthetic chemistry and physics, where isotopic substitution can have significant applications.

Nuclear Reactors

Heavy water plays a crucial role in nuclear reactors, mainly as a moderator and sometimes as a coolant. This is due to its unique ability to slow down neutrons without absorbing them as efficiently as light water can.

Some key aspects of its use in nuclear reactors include:

• The heavy nature of deuterium in D₂O allows it to decelerate neutrons, facilitating better nuclear fission reactions.
• This characteristic enables the reactor to use natural, unenriched uranium as fuel, which is a significant economic and strategic advantage.
• Heavy water reactors are considered safer and offer more flexible fuel applications.

Every nuclear reactor system is carefully designed to optimize these benefits, making heavy water an invaluable component in nuclear technology.

Deuterated Compounds

Deuterated compounds are substances in which regular hydrogen atoms are replaced by deuterium. This makes them especially useful in various scientific settings due to their unique properties, particularly in spectroscopy and tracing studies.

Consider these points about deuterated compounds:

• In NMR spectroscopy, deuterated solvents are often used because they do not interfere with the hydrogen signals being monitored in the sample molecules.
• They help in tracing the pathways of chemical reactions since they can be distinguished from hydrogen due to their heavier isotopic mass.
• Biologically, deuterated drugs can potentially have different metabolic pathways, sometimes leading to more effective or longer-lasting effects.

This versatility makes deuterated compounds highly valuable in pharmaceutical research, analytical chemistry, and advanced material sciences.