Class 10 – Science Extra Questions – Ch. 3 – Metals and Non Metals

Ans: D

Explanation: Thermal conductivity is a measure of a material’s ability to conduct heat. Metals are generally good conductors of heat. Among the given options, silver is the best conductor of heat, followed by aluminum and gold. Lead, however, has significantly lower thermal conductivity compared to the other metals listed, making it the least effective at transferring heat.
Correct Option: D

Ans: B

Explanation: Sulfur trioxide (SO3) is an acidic oxide. When acidic oxides react with water, they form acids. The reaction between sulfur trioxide and water is: SO3 + H2O → H2SO4. H2SO4 is the chemical formula for sulfuric acid. Sulfurous acid is formed from sulfur dioxide (SO2) reacting with water (SO2 + H2O → H2SO3).
Correct Option: B

Ans: A

Explanation: Brass is an alloy primarily composed of copper and zinc. The proportions of copper and zinc can vary, which affects the properties of the brass. Copper and tin form bronze, while options C and D describe other alloys or mixtures with different compositions.
Correct Option: A

Ans: C

Explanation: Zone refining is a technique used to purify materials, especially semiconductors and metals. It works by melting a narrow zone of a solid material and moving it along the length of the material. Impurities tend to concentrate in the molten zone and are thus swept to one end, leaving behind a purer solid. This process is highly effective for achieving very high levels of purity. Option A is incorrect because while it can lead to concentration, it’s not the primary application. Option B is incorrect as zone refining is not a reduction process. Option D is incorrect because while ores contain metals, zone refining is typically applied to metals already extracted from their ores, not the ore itself. Therefore, the primary application is the purification of metals.
Correct Option: C

Ans: C

Explanation: Copper pyrite, also known as chalcopyrite, has the chemical formula CuFeS2. This formula clearly indicates that it contains both copper (Cu) and iron (Fe) in its composition, making it a source of both metals. Cuprite (Cu2O) is a copper ore. Chalcoite (Cu2S) is a copper ore. Malachite (Cu2CO3(OH)2) is a copper carbonate mineral.
Correct Option: C

Ans: B

Explanation: Smelting is a process of applying heat to a ore in order to extract a base metal. It is a type of hydrometallurgical extraction that involves heating. Smelting furnaces are used. Smelting essentially reduces metal compounds in their ores by heating them. For example, iron ore is smelted in a blast furnace with coke and limestone to produce molten iron. The coke acts as a reducing agent. Therefore, the primary reason for smelting an ore is to reduce the metal compound within the ore to obtain the pure metal. Option A is incorrect because smelting is a reducing process, not an oxidizing one. Option C might be a secondary benefit of some smelting processes, but it’s not the primary reason. Option D is incorrect because smelting produces a metal, and alloys are typically formed by mixing molten metals, not by the smelting process itself, although the resulting metal might be an alloy if impurities are present.
Correct Option: B

Ans: C

Explanation: Covalent bonding occurs when atoms share electrons, typically between nonmetals. Ionic bonding occurs when atoms transfer electrons, typically between a metal and a nonmetal. MgCl2 is formed between a metal (Mg) and a nonmetal (Cl), so it exhibits ionic bonding. KBr is formed between a metal (K) and a nonmetal (Br), so it exhibits ionic bonding. H2O is formed between two nonmetals (H and O), so it exhibits covalent bonding. LiF is formed between a metal (Li) and a nonmetal (F), so it exhibits ionic bonding.
Correct Option: C

Ans: D

Explanation: Calcination is a thermal decomposition process where metal carbonates are heated to high temperatures in the absence of air or with limited air supply, causing them to break down into metal oxides and carbon dioxide. Smelting is used to extract metals from their ores, often involving reduction with carbon at high temperatures. Electrolysis is used to decompose ionic compounds, typically in molten form or dissolved in a solvent, into their constituent elements. Roasting is the heating of metal sulfides in the presence of excess air to convert them into oxides. Therefore, calcination is the process specifically used to convert metal carbonates into metal oxides.
Correct Option: D

Ans: B

Explanation: Amphoteric oxides are oxides that can react with both acids and bases. Metal oxides are typically basic, while non-metal oxides are typically acidic. However, some metal oxides exhibit amphoteric behavior. Zinc oxide (ZnO) is a classic example of an amphoteric oxide. It reacts with acids to form zinc salts and water, and it reacts with strong bases to form zincate salts and water. Magnesium oxide (MgO) is a basic oxide and reacts with acids but not with bases. Potassium oxide (K2O) is a strongly basic oxide and reacts with water to form potassium hydroxide, which is a strong base. Sulfur dioxide (SO2) is an acidic oxide and reacts with water to form sulfurous acid, and it reacts with bases. Therefore, zinc oxide is the only amphoteric oxide among the given options.
Correct Option: B

Ans: D

Explanation: Smelting is a process of applying heat to ore in order to extract a base metal. It is a form of extractive metallurgy. The process of smelting involves heating the ore to a high temperature, often in the presence of a reducing agent, to separate the metal from its ore. Therefore, smelting is a technique used to increase the metal content of an ore by extracting the metal. Gravity separation, froth flotation, and electromagnetic separation are all methods used to concentrate the ore by removing impurities, thus increasing the metal content of the remaining material. Smelting, however, is the actual extraction of the metal from the concentrated ore.
Correct Option: D