Class 10 Science Chapter 3 MCQ

Nitrogen is an inert gaseous non-metal whose presence in air reduces the rate of combustion and makes it safe.

Graphite is a good conductor of electricity and heat. Graphite has weak intermolecular forces between its layers. Hence it has de-localised electrons. As electrons are free to move through its structure, it conducts heat and electricity well.

Silver metal is the best conductor of heat. Copper and Aluminium metals are also very good conductors of heat. Mercury metal is also a poor conductor of heat. The poorest conductor of heat among the metals is lead.

Magnesium metal reacts with cold water to form magnesium oxide and evolves hydrogen gas is an incorrect statement. Magnesium when reacts with water gives magnesium hydroxide and hydrogen gas. Reaction of metals and water generally produce hydrogen gas and their respective hydroxide. For example, sodium metal reacts with water to produce sodium hydroxide and liberates hydrogen gas.

Gallium and cesium metals also have low melting points (of 30°C and 28°C respectively). The melting points of gallium and cesium metals are so low that they start melting in hand (by the heat of our body).

Non-metals are brittle which means that non-metals break into pieces when hammered or stretched. For example, sulphur and phosphorus are solid non-metals which are non-malleable and non-ductile.

An electrolytic cell consists of positively charged anode and negatively charged cathode. Positively charged ions (cations) are deposited at negatively charged cathode. Negatively charged ions (anions) are deposited at positively charged anode.

An alloy is a homogeneous mixture. Alloy is a homogeneous mixture of two or more metals. For example, brass is an alloy of copper and zinc. Stainless steel is an alloy made with combination of iron with chromium with nickel.

Test tube C contains chemical mixture called aqua-regia. It is a mixture of concentrated HCl and concentrated HNO3 in the ratio of 3:1. Aqua-regia dissolves gold and platinum in it while hydrochloric acid and nitric acid do not.

Copper gets green coating due to the formation of a mixture of copper carbonate and copper hydroxide when it reacts with carbon dioxide gas and moisture present in air. This is called tarnishing of copper. You can easily understand by this equation: 2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3

Magnesium metal does not react with cold water. Magnesium reacts with hot water to form magnesium hydroxide and hydrogen: You can easily understand by this equation: Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g) Magnesium + Water (hot) → Magnesium hydroxide + Hydrogen

Coating iron or steel with a layer of zinc prevents it from rusting. This process is called galvanization. Water pipes are also galvanized to protect them from corrosion.

Silver articles turn black after prolonged exposure to air due to the reaction of sulphur present in air. Silver reacts with sulphur to form dark grey to black silver sulphide.

Here, all the statements are correct. Hence, your answer will be option [D].

Gold (Ag) and copper (Cu) obtained after extraction is in impure form. So, metals Au (gold) and Cu (copper) are refined by electrolytic refining. Other than gold and copper, electrolytic refining is used for metals such as Zn and Ag. Sodium (Na) and potassium (K) are extracted by electrolytic reduction. Metals obtained after electrolytic reduction are in pure form.

In solid state, ions in ionic compounds are not free to move. Thus, such compounds do not show electrical conductivity in solid state. Whereas, in molten state, ions are free to move and hence conduct electricity.

Here, all the statements are correct. Hence, your answer will be option [D].

Non-ionic compounds are those that have covalent bonds. Hydrochloric acid (HCl) and carbon tetrachloride (CCl4) form covalent due to sharing of a pair of electrons between two atoms. Whereas sodium chloride (NaCl) and potassium chloride (KCl) form ionic compounds as they consist of positive and negative ions.

Here, all the statements are correct. Hence, your answer will be option [D].

When calcium is treated with water, it reacts with water vigorously and to produce a cloudy white precipitate of calcium hydroxide and hydrogen gas is released as bubbles. You can easily understand by this equation: Ca(s) + 2 H2O(g) → Ca(OH)2(s) + H2(g) Sometimes hydrogen bubbles get stuck to the surface of calcium metal making it light and thus calcium starts floating. This reaction is exothermic in nature.

When steam is passed over iron for a long time, it gives iron oxide (Fe3O4) and hydrogen gas. You can easily understand by this equation: 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

Carbon is a non-metal that can exist in different forms. Each form is called an allotrope. Diamond, an allotrope of carbon, is the hardest natural substance known and has a very high melting and boiling point. Note: Graphite, another allotrope of carbon, is a conductor of electricity.

Na (sodium) and Ca(calcium) react with water vigorously. Mg (Magnesium) reacts with water less vigorously than that of calcium and sodium. Fe (Iron), on the other hand, does not react with cold as well as hot water instantly. But when the iron is kept in contact with water for a long time, rusting of iron happens.

Copper metal is more reactive than silver metal (Ag), so a displacement reaction will take place between AgNO3 solution and copper metal. In option A: Copper metal is less reactive than sodium metal (Na), so no displacement reaction will occur between NaCl solution and copper metal. In option B: Aluminium metal is less reactive than magnesium metal (Mg), so no displacement reaction will take place between MgCl2 solution and Aluminium metal. In option C: Silver metal is less reactive than iron metal (Fe), so no displacement reaction will occur between FeSO4 solution and silver metal.

The ability of metals to be drawn into thin wire is called ductility. It is one such property of metals that is used to make wires from metals. Metals such as copper have high ductility and thus can be drawn into long and thin wires without breaking.