Question

What is formed when calcium carbide reacts with heavy water? (a) \(\mathrm{CaD}_{2}\) (b) \(\mathrm{C}_{2} \mathrm{D}_{2}\) (c) \(\mathrm{Ca}_{2} \mathrm{D}_{2} \mathrm{O}\) (d) \(\mathrm{CD}_{2}\)

Short answer

(b) \(\mathrm{C}_{2} \mathrm{D}_{2}\)

Step-by-step solution

Understand the Reaction

Calcium carbide (CaC₂) reacts with water to produce acetylene gas (C₂H₂) and calcium hydroxide (Ca(OH)₂). In this problem, we need to consider the reaction with heavy water, which contains deuterium (D) instead of hydrogen (H). So, the products will include a deuterated version of acetylene, where D replaces H.

Write the Balanced Chemical Equation

When calcium carbide reacts with heavy water, the reaction can be represented as:\[\mathrm{CaC}_{2} + 2\mathrm{D}_{2}\mathrm{O} \rightarrow \mathrm{C}_{2}\mathrm{D}_{2} + \mathrm{Ca(OD)}_{2}.\] This equation indicates that calcium carbide reacts with deuterium oxide (D₂O), forming deuterated acetylene (C₂D₂) and calcium deuteroxide (Ca(OD)₂).

Identify the Products

The main product of interest is the gas formed. From the balanced equation, we see that deuterated acetylene (C₂D₂) is produced. This corresponds to option (b) in the given choices.

Key concepts

Calcium Carbide

Calcium carbide is a chemical compound with the formula \( \text{CaC}_2 \). It is primarily used for producing acetylene gas, which is a valuable raw material in the chemical industry and also used for welding and cutting metals. Calcium carbide itself is a grayish-black crystalline solid with a strong odor because it reacts easily with water.
When calcium carbide interacts with water, the reaction releases acetylene gas and calcium hydroxide as by-products. This reaction happens because water breaks the carbon-calcium bond, releasing acetylene.

• Used in the production of acetylene gas.
• Essential for welding and cutting applications.
• Reacts readily with water.

Understanding calcium carbide is crucial to grasping how it behaves during chemical reactions, especially when we consider its reaction with heavy water in this exercise.

Heavy Water

Heavy water, known chemically as deuterium oxide (\( \text{D}_2\text{O} \)), is similar to regular water but with a distinctive difference. In heavy water, the usual hydrogen atoms are replaced by deuterium atoms, a heavier isotope of hydrogen with one proton and one neutron in its nucleus. This subtle change gives heavy water distinct physical and chemical properties compared to ordinary water.
Heavy water is often used in nuclear reactors as a neutron moderator. In this reaction, it replaces ordinary water to form products that contain deuterium rather than regular hydrogen. Understanding heavy water is important as it showcases how isotopic substitution can lead to different chemical behaviors and products.

Deuterium

Deuterium is an isotope of hydrogen represented by the symbol \( \text{D} \). Unlike regular hydrogen, which has just one proton in its nucleus, deuterium has one proton and one neutron, making it heavier. While deuterium behaves chemically like hydrogen, its additional neutron allows it to form bonds that are slightly different.
In this exercise, deuterium is a key player as it replaces hydrogen in the chemical reaction between calcium carbide and heavy water. This substitution results in the formation of deuterated compounds, such as deuterated acetylene (\( \text{C}_2\text{D}_2 \)). Recognizing the role of deuterium as a hydrogen isotope is vital in understanding isotopic effects in chemistry.

Chemical Equation Balancing

Balancing chemical equations is essential to accurately represent a chemical reaction. Each side of the equation must have the same number of atoms for each element, ensuring the law of conservation of mass. In this problem, we see the balanced reaction: \[ \text{CaC}_{2} + 2\text{D}_{2}\text{O} \rightarrow \text{C}_{2}\text{D}_{2} + \text{Ca(OD)}_{2} \]. Here, the equation illustrates how calcium carbide reacts with two molecules of deuterium oxide to form deuterated acetylene and calcium deuteroxide.
Balancing equations is crucial because it reflects the actual proportions in which reactants combine and products form. A balanced equation helps predict the amounts of reactants needed and products formed, demonstrating a fundamental skill in chemistry.

Product Formation in Reactions

In any chemical reaction, understanding product formation is vital. It involves determining the substances produced from the reactants under specific conditions. In our given reaction between calcium carbide and heavy water, deuterated acetylene (\( \text{C}_2\text{D}_2 \)) and calcium deuteroxide are the primary products. This type of formation highlights the importance of understanding the nature of reactants to predict accurately the resulting substances.
Product formation analysis helps chemists know what to expect from a reaction, design experiments effectively, and apply the results in practical applications. Recognizing how different conditions, like substituting heavy water, alter products is an important aspect of chemical science.