67th Prelims 2022

Explanation:

A magnifying glass typically uses a convex lens to magnify objects. The convex lens is thicker at the center and thinner at the edges, causing light rays to converge and appear larger when they pass through the lens. This lens shape allows the magnifying glass to create a magnified virtual image of an object when held close to the eye.

Explanation:

Paramagnetism is a type of magnetism that occurs in substances weakly attracted by a magnetic field and do not retain magnetism once the external field is removed. This arises due to unpaired electrons. Platinum has unpaired electrons and thus exhibits paramagnetic behavior.

Explanation:

The nucleus of an atom consists of protons and neutrons. It is the central part of an atom that contains most of its mass and positive charge. Electrons orbit the nucleus in shells and are not part of it.

Explanation:

Smelting is a metallurgical process in which a metal is obtained in a fused or molten state by heating the ore with a reducing agent in a furnace. Roasting, calcination, and froth flotation are other metallurgical processes with different purposes.

Explanation:

Both statements are correct. Adding a non-volatile solute like salt decreases vapor pressure, increasing boiling point and decreasing freezing point. Adding volatile methanol increases vapor pressure, lowering the boiling point.

Explanation:

Brass is an alloy primarily composed of copper and zinc. Copper is usually the main component, while zinc is added to achieve desired properties. Other combinations like iron and nickel are not brass.

Explanation:

Methane (CH4) is the primary component of biogas, produced from the breakdown of organic matter in an anaerobic environment. It is used as a cooking fuel and to generate electricity.

Explanation:

Strontium compounds, such as strontium nitrate or carbonate, produce a bright red color when ignited in fireworks due to specific electronic transitions in the strontium atoms.

Explanation:

Halophytes are plants adapted to high-salt environments like saline soils and coastal areas. They have mechanisms to tolerate or excrete excess salt.

Explanation:

Quicklime is calcium oxide (CaO), produced by heating calcium carbonate (CaCO3), releasing CO2. Ca(OH)2 is slaked lime, CaCl2 is calcium chloride, and CaCO3 is limestone.

Explanation:

Initially, rust formation increases weight as oxygen combines with iron. Over time, rust can flake off and reduce weight, so overall it increases then decreases.

Explanation:

None of the listed elements is commonly called 'White metal'. White metal refers to a group of silvery alloys made of tin, antimony, etc., used in jewelry and decorative items.

Explanation:

Only statement 1 is correct. Noble metals like gold, silver, and platinum resist corrosion and are found in pure form. Uranium, lead, and brass are not noble metals.

Explanation:

Fungi lack chlorophyll and cannot perform photosynthesis. They obtain nutrients by decomposing organic matter or forming symbiotic relationships.

Explanation:

Pollination is the transfer of pollen grains from anther to stigma, which can occur via wind, water, or animals. Other options describe subsequent processes or related activities.

Explanation:

Plants absorb essential nutrients like nitrogen, phosphorus, and potassium from soil through roots. Light and chlorophyll are involved in photosynthesis, not nutrient absorption.

Explanation:

These are gymnosperms, which produce seeds but not flowers. Seeds are 'naked' and not enclosed in fruits.

Explanation:

Malaria is treated with Chloroquine. The other pairs are incorrect: ATS is diagnostic for TB, BCG is for tuberculosis, and Thiamine prevents beriberi, not scurvy.

Explanation:

Earthworms lack red blood cells and rely on coelomic fluid for gas transport. Snakes, peacocks, and frogs all have red blood cells.

Explanation:

Carbohydrates are broken down to glucose, a monosaccharide that cells use for energy through glycolysis and the Krebs cycle.