Chemistry: Inorganic Chemistry: UPSC Previous Year Questions (Science and Technology)

Explanation

Nichrome is an alloy of nickel and chromium, often used in heating elements due to its high resistance to heat and corrosion. It is ductile, allowing it to be drawn into wires for use in various applications. It is considered hard relative to other ductile materials, which is why it finds applications in industrial heating where both durability and flexibility are important. Options (a), (b) and (c) are incorrect:

Carborundum (silicon carbide) is very hard but not ductile; it is brittle. It is mainly used as an abrasive material. Cast iron is hard but brittle, and it cannot undergo significant deformation without breaking. While Tungsten is harder, it is less ductile compared to Nichrome in practical scenarios. Tungsten’s brittleness increases under certain conditions, making Nichrome a more balanced choice for being both hard and ductile.

Explanation

Statement 1 is correct: Hard water, rich in calcium and magnesium, can contribute to dietary intake of these minerals, but prolonged consumption may lead to kidney stones and urinary tract issues, particularly for susceptible individuals. Research indicates that high calcium levels can affect renal function.

Statement 2 is correct: When hard water is used with soap, it forms soap scum, which reduces lather and makes washing less effective. Scum leaves residue on clothes, making them feel rough and unclean. This can also increase detergent usage.

Statement 3 is correct: The minerals in hard water like calcium carbonate and magnesium salts, form scale in boilers and pipes, reducing thermal efficiency and leading to energy wastage and equipment failure.

Statement 4 is correct: Continuous irrigation with hard water results in soil salinization, decreasing permeability and crop yield. Excess minerals like calcium and magnesium hinder plant nutrient absorption due to reduced soil’s permeability. Directions: The following two Items consist of statements. One labeled as the ‘Assertion (A)’ and the other as ‘Reason (R)’. You have to answer these items using the code given below: (1999)

Explanation

A is matched with 4: Blue vitriol is the common name for copper sulphate, known for its bright blue color. B is matched with 3: Epsom salt is the common name for magnesium sulphate, often used in bath salts and as a laxative. C is matched with 1: Baking soda is sodium bicarbonate, used in cooking as a leavening agent. D is matched with 2: Caustic soda is the common name for sodium hydroxide (NaOH), a strong base used in industrial applications like soap making.

Explanation

A is matched with 2: Potassium bromide is widely used in the photographic industry. It acts as a restrainer in photographic developers and is used in the preparation of photographic emulsions. B is matched with 4: Potassium nitrate, also known as saltpeter, is a key ingredient in gunpowder due to its oxidizing properties. It releases oxygen during combustion, aiding in the rapid burning of other materials. C is matched with 1: Potassium sulphate is an important fertilizer that supplies potassium, a vital nutrient for plant growth. It is especially used in chloride-sensitive crops like potatoes, tobacco, and citrus fruits because it contains no chloride ions. D is matched with 3: Monopotassium tartrate is extensively used in baking. It helps stabilize egg whites, prevents sugar crystallization, and is a component of baking powder, contributing to the leavening process in cakes and bread.

Explanation

An amalgam is an alloy of mercury with another metal. While many metals can form amalgams, iron does not readily form one because it has a very low affinity for mercury under normal. On the other hand, metals like zinc, copper, and magnesium can form amalgams.

Explanation

Fluorine is the most reactive halogen because:

Small Atomic Size: Fluorine has the smallest atomic radius among halogens, leading to a strong attraction for electrons. High Electronegativity: It is the most electronegative element in the periodic table, making it highly effective in gaining electrons. Low Bond Dissociation Energy: The F-F bond in molecular fluorine is weak due to electron repulsion between the two small atoms, which makes it highly reactive. Reactivity Trend in Halogens:

Fluorine > Chlorine > Bromine > Iodine

Explanation

Option (b) is correct: Chromium is added to iron to produce stainless steel and other high-performance alloys. It provides resistance to oxidation and high temperatures while also increasing hardness and abrasion resistance. Chromium’s ability to form a protective oxide layer makes it essential for producing steel that can withstand harsh conditions. Options (a), (c) and (d) are incorrect:

Aluminium is used for lightweight and corrosion-resistant alloys but not for high-temperature or abrasion resistance. Nickel primarily enhances toughness and corrosion resistance but does not directly improve abrasion resistance as much as chromium. Tungsten contributes to high-temperature strength and wear resistance, especially in tool steels, but chromium is the primary alloying element for the application.

Explanation

Micronutrients are essential elements required by plants in very small quantities (typically less than 100 mg/ kg of plant dry matter). Despite their minimal requirement, these nutrients play a critical role in various physiological and biochemical processes necessary for plant growth and development. Sodium is not considered an essential micronutrient for most plants. It may play a role in some specific plants, such as C₄ plants, but it is not universally required as a micronutrient. Other important micronutrients are Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo), Chlorine (Cl), Nickel (Ni).