Class 10 Science Chapter 3 MCQ

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

Al (Aluminium) forms amphoteric oxides. An amphoteric oxide acts both as an acid and as a base.

The major non-metals in the earth’s crust in the decreasing order of their abundance are: Oxygen, Silicon, Phosphorus and Sulphur.

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.

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.

Na (sodium) possesses all the above properties. It is too soft and can be cut with a knife. It is also very reactive and reacts with oxygen or moisture present in air and produce sodium hydroxide which is highly exothermic reaction producing a lot of heat. It also reacts with water vigorously and burns due to the formation of hydrogen gas. That is why sodium is stored in kerosene oil to prevent any reaction.

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.

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.

Sodium and calcium are very reactive metals and are placed towards the top of the reactivity series. These are produced by the electrolysis of their molten chlorides. The metal ions are deposited at negatively charged cathode and chlorine is deposited at positively charged anode.

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.

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

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

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

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

Gold (Au) and silver (Ag) are not reactive or very less reactive. These metals are called noble metals. Thus, these are placed at the bottom of the reactivity series. Since gold and silver are least reactive of all the metals, these are found in free state in nature.

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].

Aqua-regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. Aqua-regia being a very strong acid dissolves gold in it.

Aqua regia, (Latin for ‘royal water’) is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It can dissolve gold, even though neither of these acids can do so alone. Aqua regia is a highly corrosive, fuming liquid. It is one of the few reagents that is able to dissolve gold and platinum.

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.

Metals like potassium and sodium react violently with cold water. In case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire. You can easily understand by this equation: 2K(s) + 2H2O(l) → 2KOH(aq) + H2 (g) + heat energy 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) + heat energy

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.

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.

Metals generally do not show dullness. Metals such as gold and silver usually are shiny rather than dull.