1 PUC Chemistry Question Paper

Explanation: This question asks you to identify the specific oxide of chlorine that is widely applied in industrial bleaching processes and purification of water supplies. Chlorine forms several oxides, each with distinct chemical properties and stability. Among these, some act as strong oxidizing agents capable of breaking down colored impurities and harmful microorganisms. The effectiveness of a bleaching agent depends on its ability to release reactive oxygen or chlorine species that can disrupt chromophores and microbial cell structures. In industrial applications like paper and textile processing, such compounds help remove unwanted coloration without severely damaging the material. In water treatment, similar oxidative behavior helps eliminate bacteria and other pathogens. By comparing the properties of different chlorine oxides—such as their stability, reactivity, and oxidizing strength—you can determine which one is suitable for these purposes. The correct choice will be the oxide known for controlled yet powerful oxidation, making it both efficient and practical for large-scale use in bleaching and disinfection.

Explanation: This question focuses on identifying a compound used in the detection or quantitative estimation of carbon monoxide gas. Carbon monoxide is a colorless, odorless gas that can be dangerous, so reliable detection methods are essential. Certain chemical reagents react specifically with carbon monoxide, undergoing measurable changes that allow scientists to determine its concentration. These reagents often function through oxidation-reduction reactions, where carbon monoxide is oxidized while the reagent is reduced or transformed into another compound. The selection of such a reagent depends on its sensitivity, specificity, and stability under testing conditions. Some compounds are particularly useful because they provide clear and quantifiable results, either through color change or formation of a new substance. By recalling standard laboratory reagents associated with gas analysis and their chemical behavior, you can identify which compound is commonly used for this purpose. The correct option will be the reagent known for its reliability in estimating carbon monoxide levels in analytical Chemistry.

Explanation: This question requires evaluating multiple statements describing the physical and chemical properties of chlorine gas. Chlorine is a halogen belonging to Group 17 of the Periodic Table and exists as a diatomic Molecule under standard conditions. It has distinct physical characteristics such as color, odor, and density, which help in its identification. Its greenish-yellow appearance and sharp, irritating smell are well-known features. Additionally, chlorine is denser than air, allowing it to settle in lower areas when released. These properties are important in both industrial handling and safety considerations. To determine the correct choice, each statement should be examined carefully and compared with known standard properties of chlorine. The correct selection will be the one that includes only accurate descriptions of chlorine’s observable and measurable characteristics.

Explanation: This question focuses on the various practical uses of chlorine across different industries. Chlorine is a highly reactive halogen and serves as a powerful oxidizing agent, which makes it useful in several chemical processes. It plays a role in metallurgical extraction processes, especially in separating certain Metals from their ores. Additionally, chlorine is widely used in bleaching processes due to its ability to remove color by oxidation. Another major application is in water treatment, where it helps disinfect drinking water by killing harmful microorganisms. When evaluating the given options, it is important to consider the versatility of chlorine and its involvement in diverse industrial and environmental processes. The correct choice will reflect the wide range of its applications rather than a single isolated use.

Explanation: This question examines the different applications of hydrochloric Acid, a strong mineral Acid commonly used in laboratories and industries. Hydrochloric Acid is highly reactive and plays a key role in chemical synthesis and industrial processes. It is used in the production of various compounds and also in processing natural materials like bones to extract useful substances. In addition, it has applications in medicine and laboratory work, particularly in adjusting pH and preparing reagents. Its corrosive nature allows it to clean surfaces and remove impurities effectively. To answer the question, each listed use should be evaluated for its correctness based on known industrial and laboratory practices. The correct option will encompass all valid applications associated with hydrochloric Acid.

Explanation: This question deals with a chemical reaction between slaked lime and chlorine gas. Slaked lime, chemically known as calcium hydroxide, reacts with chlorine in a process commonly used for preparing bleaching powder. This reaction involves both oxidation and substitution processes, leading to the formation of a compound containing chlorine in more than one oxidation state. The product formed is widely used for bleaching and disinfecting purposes. Understanding the nature of the reactants and the type of reaction helps in predicting the product. By analyzing how chlorine interacts with hydroxide ions and calcium ions, the resulting compound can be identified. The correct choice corresponds to the compound formed through this industrially important reaction.

Explanation: This question refers to a well-known qualitative test involving iodine. Iodine is often used as an indicator because it forms characteristic colored complexes with certain substances. One of the most notable reactions is its interaction with a specific polysaccharide, where iodine molecules get trapped within the helical structure, producing a deep blue color. This reaction is commonly used in laboratories to test for the presence of that substance. Other given options may not produce such a distinct color change with iodine. To determine the correct answer, recall which compound forms this unique colored complex with iodine and is widely used in chemical identification tests.

Explanation: This question examines the reaction of fluorine with a dilute solution of sodium hydroxide under cold conditions. Fluorine is the most reactive halogen and exhibits behavior that differs significantly from other halogens. When it reacts with alkali, it undergoes a disproportionation reaction, meaning it is simultaneously reduced and oxidized to form different products. The nature of the products depends on reaction conditions such as temperature and concentration. Under cold and dilute conditions, specific compounds are formed due to controlled reactivity. To answer this question, one must understand the unique Chemistry of fluorine and how it interacts with hydroxide ions. The correct option represents the SET of products typically obtained in this reaction scenario.

Explanation: This question explores the reaction of iodine with hot, concentrated sodium hydroxide. Iodine, being a less reactive halogen compared to fluorine and chlorine, undergoes disproportionation reactions under strong alkaline conditions. In this process, iodine is both oxidized and reduced, leading to the formation of two different iodine-containing products along with water. The products formed depend on the temperature and concentration of the alkali used. Under hot and concentrated conditions, higher oxidation state compounds are typically formed. By understanding the redox behavior of iodine and the influence of reaction conditions, the resulting products can be predicted. The correct answer corresponds to the combination of compounds formed in this specific reaction.

Explanation: This question asks you to compare the oxidizing strength of different oxoacids of halogens. Oxoacids are Acids that contain oxygen along with the halogen Atom, and their oxidizing ability depends on the oxidation state of the central Atom and the stability of the products formed after reduction. Generally, compounds where the central Atom is in a higher oxidation state tend to act as stronger oxidizing agents. However, other factors such as bond strength and Molecular stability also play a role. By analyzing the oxidation states and structural characteristics of the given oxoacids, you can determine which one has the greatest tendency to accept electrons. The correct choice will be the Acid with the highest effective oxidizing capability among the options.

Explanation: This question focuses on arranging chlorine oxoacids in order of increasing Acid strength. The acidity of oxoacids depends primarily on the oxidation state of the central Atom and the number of oxygen atoms attached to it. As the number of oxygen atoms increases, the electron-withdrawing effect becomes stronger, stabilizing the conjugate Base and enhancing acidity. This leads to a systematic trend in Acid strength among chlorine oxoacids. By examining the structure and oxidation state of chlorine in each compound, the correct order can be determined. The correct option will reflect the gradual increase in acidity based on these structural and electronic factors.

Explanation: This question requires analyzing the Molecular structure of a chlorine oxide to determine the total number of chlorine–oxygen bonds present. Cl₂O₇ is a higher oxide of chlorine with a complex structure consisting of two chlorine atoms connected through oxygen atoms. Each chlorine Atom is bonded to multiple oxygen atoms, and there is also a bridging oxygen between them. By drawing or visualizing the Molecular structure, one can count the number of individual Cl–O bonds present in the Molecule. Understanding the Bonding pattern and oxidation state helps in constructing the correct structure. The correct answer corresponds to the total count of these bonds in the Molecule.

Explanation: This question asks about the product formed when chlorine gas reacts with mercuric oxide at an elevated temperature. Chlorine is capable of forming different oxides depending on reaction conditions such as temperature and the nature of the reacting substance. Mercuric oxide acts as an oxidizing agent and facilitates the formation of a chlorine oxide. At higher temperatures, the reaction pathway favors the formation of a specific oxide with a particular oxidation state of chlorine. To determine the correct product, it is important to consider how chlorine behaves under thermal conditions and how oxygen from the oxide is transferred. The correct choice corresponds to the stable oxide formed under these reaction conditions.

Explanation: This question focuses on identifying the acid capable of reacting with glass surfaces. Glass is primarily composed of silica, which is generally resistant to most Acids. However, there exists a particular acid that can react with silica to form volatile or soluble products, thereby corroding or etching the surface. This unique property makes the acid useful in industries for engraving designs on glass and cleaning glassware. The reaction involves breaking the strong silicon–oxygen bonds present in silica. By recalling which acid has the ability to attack silica effectively, the correct option can be identified. The correct choice is the acid known for this distinct and specialized chemical behavior.

Explanation: This question deals with historical chemical nomenclature. In earlier times, chemists used different names for substances based on their properties and behavior. The term “muriatic acid” was historically used for a well-known acid, and “oxy-muriatic acid” referred to a related substance believed to contain oxygen. Later discoveries clarified that this substance was actually an element rather than a compound containing oxygen. Understanding the Evolution of chemical naming and the shift from old terminology to modern nomenclature is key to answering this question. By linking historical names with their modern equivalents, the correct compound can be identified.

Explanation: This question examines the chemical methods used to produce chlorine gas in the laboratory. Chlorine can be generated by the oxidation of hydrochloric acid using strong oxidizing agents. In such reactions, chloride ions lose electrons and form chlorine gas, while the oxidizing agent is reduced. The efficiency of this reaction depends on the strength of the oxidizing agent and the reaction conditions. Several oxidizing agents are capable of carrying out this transformation. To determine the correct answer, it is necessary to identify which substances can oxidize hydrochloric acid effectively to release chlorine gas. The correct option includes those reagents known for this purpose.

Explanation: This question involves determining the hybridization of the central Atom in a Molecular structure. In BrF₅, bromine is bonded to five fluorine atoms and also possesses one lone pair of electrons. To find the hybridization, the total number of electron pairs (Bonding and lone pairs) around the central Atom must be considered. This total determines the type of hybrid orbitals formed and the geometry of the Molecule. With six electron pairs, the arrangement corresponds to an octahedral electron geometry, though the Molecular shape differs due to the lone pair. By applying VSEPR theory and hybridization concepts, the correct hybridization can be identified.

Explanation: This question requires comparing the reducing strength of hydrogen halides. Reducing power refers to the ability of a substance to donate electrons. In hydrogen halides, this ability depends on the bond strength between hydrogen and the halogen Atom. As we move down the group, the bond length increases and bond strength decreases, making it easier for the compound to release electrons. This results in an increase in reducing power. Other factors such as stability of the resulting halogen species also play a role. By analyzing Periodic trends and bond characteristics, the correct increasing order can be determined. The correct option reflects the gradual increase in reducing ability from one acid to another.