SSC CGL Tier 2 Level Test: Chemistry- 2 - SSC CGL MCQ

Elements are pure substances that cannot be chemically decomposed (e.g., oxygen, iron). Compounds have a fixed composition by mass (e.g., water is always 2:16 H:O by mass), making both statements correct.

Silicon is a metalloid, exhibiting properties of both metals and non-metals. Sodium and calcium are metals, while sulfur is a non-metal.

In a redox reaction, the oxidizing agent gains electrons (is reduced), while the reducing agent loses electrons (is oxidized). Catalysts speed up reactions, and electrolytes conduct electricity in solutions.

Carbon has a valency of 4, forming four single covalent bonds with hydrogen atoms in methane (CH₄) to achieve a stable octet.

Catalysts speed up reactions by lowering activation energy without being consumed. They do not change the chemical composition of products, making Statement 2 incorrect.

Argon, a noble gas, is used in welding to provide an inert atmosphere. Nitrogen, oxygen, and hydrogen are not noble gases.

The Bronsted-Lowry theory defines an acid as a proton (H⁺) donor and a base as a proton acceptor. Releasing hydroxide ions is part of the Arrhenius theory, and accepting an electron pair relates to the Lewis theory.

Ammonium nitrate (NH₄NO₃) is widely used as a nitrogen-rich fertilizer. Sodium chloride is table salt, sodium bicarbonate is baking soda, and calcium carbonate is used in lime.

Corrosion of iron (rusting) forms iron oxide (Fe₂O₃) in the presence of oxygen and moisture. Galvanization coats iron with zinc, which acts as a sacrificial anode, preventing corrosion.

Diamond has a tetrahedral, three-dimensional covalent structure, making it extremely hard. Graphite has layered sheets, fullerene has cage-like molecules, and graphene is a single layer of carbon atoms.

Smelting involves heating ore to extract metal, often with a reducing agent (e.g., carbon). Roasting heats ore in oxygen, calcination removes volatile impurities, and electrolysis is used for specific metals like aluminum.

Ethene (C₂H₄) is an alkene with a carbon-carbon double bond. Ethane, methane, and propane are alkanes with single bonds.

Eutrophication results from nutrient overload, causing algal blooms. BOD measures oxygen needed by microbes to break down organic matter, indicating water pollution levels.

Brass is an alloy of copper and zinc. Copper and tin form bronze, while iron is not typically used in brass.

Green chemistry aims to design safer chemicals and sustainable processes to minimize environmental impact. The other options contradict its principles.

Acetic acid (CH₃COOH) contains a carboxylic acid group (-COOH). Hydroxyl is in alcohols, aldehyde in aldehydes, and ketone in ketones.

Carbon monoxide (CO) is a toxic pollutant from incomplete combustion in vehicles. Smog, particularly photochemical smog, forms when sunlight reacts with NOx and VOCs, producing ozone and other pollutants.

Baking soda is sodium bicarbonate (NaHCO₃). NaCl is table salt, Na₂CO₃ is washing soda, and CaCO₃ is limestone.

Decomposition of calcium carbonate (CaCO₃ → CaO + CO₂) requires heat, making it endothermic. Combustion, neutralization, and respiration are exothermic, releasing heat.

Aspirin (acetylsalicylic acid) is an analgesic used to relieve pain. Penicillin and streptomycin are antibiotics, and insulin is a hormone for diabetes management.