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.

Atomic number of X is 10, so this must be Ne (Neon), a noble or inert gas. This gas has octate configuration. Atomic number of Y is 2 + 8 + 7 = 17, so this must be chlorine (Cl). Chlorine is a non–metal. Non-metals have 5 to 7 electrons in their valence shell. Atomic number of Z is 2 + 8 + 2 = 12, so this must be Magnesium (Mg). Magnesium is a metal. Metals have 1 or 2 electrons in their valence shell.

Compound Z does not show the property of “Has low melting point”. As compound Z is formed because of transfer of electrons between X and Y, hence Z is an ionic compound. Such compounds do not have low melting point. Bonds in ionic compounds are very strong. Therefore, a lot of energy is needed to break them. This is the reason why ionic compounds have high melting and boiling points.

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.

Steel contains non-metal as one of its constituents. Steel is an alloy made by combining iron and other elements mainly carbon. Carbon gives strength to iron. It is used to make buildings, ships, automobiles, machines, appliances.

The metals which have high densities, we mean that metals are heavy substances. For example, the density of iron is 7.8 g/cm3 which is quite high. So, iron metal is a heavy substance. There are, however, some exceptions. For example, sodium and potassium metals have low densities (of 0.97 g/cm3 and 0.86 g/cm3 respectively). They are very light metals.

Only one non-metal carbon (in the form of diamond) is very hard. In fact, diamond (which is an allotropic form of carbon) is the hardest natural substance known

Mercury (Hg) is the only metal which is found in liquid state at room temperature. All other metals are solid at room temperature. It also has the lowest melting point.

Potassium reacts violently with cold water to form potassium hydroxide and hydrogen gas: You can easily understand by this equation: 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) + Heat Potassium + Water(cold) → Potassium hydroxide + Hydrogen The reaction of potassium metal with water is highly exothermic (heat producing) due to which the hydrogen gas formed during the reaction catches fire immediately. Thus, potassium is a very, very reactive metal.

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

Alloying elements enhance the structure and properties such as durability, strength and toughness of the metal. It makes them corrosion resistant. Stainless steel is an alloy of iron, nickel and chromium.

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

Oxygen (O) is a non-metal which forms negatively charged oxide ions (O2–) by gaining electrons.

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

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.

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.

Pure gold, known as 24 carat gold, is very soft. It is, therefore, not suitable for making jewellery. It is alloyed with either silver or copper to make it hard. Generally, in India, 22 carat gold is used for making ornaments. It means that 22 parts of pure gold is alloyed with 2 parts of either copper or silver.

Does not give hydrogen gas on reacting with metals. Nitric acid is a strong oxidizing agent. It oxidizes hydrogen produced in the reaction to water and nitric acid itself is reduced to any of these nitrogen oxides [N2O (nitrous oxide), NO (nitric oxide) or NO2 (nitrogen dioxide)]. On the contrary, magnesium and manganese reacts with dilute nitric acid to give salt and hydrogen gas.

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.

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.

Aluminium has good thermal conductivity and high melting point. As a good conductor of heat, it helps in heat transfer and cooking of food. With the high melting point, one can cook food in such utensils at higher temperatures and the Aluminium utensils can withstand such higher temperatures without being melted by the heat.

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.