Science M.C.Q-[Che-1M]

3. An amphoteric oxide.

Explanation:

Zinc oxide can react with both acids and bases to form salt and water.

1. Roasting.

Explanation:

Zinc blende (zinc sulphide or ZnS) is a sulphide ore of zinc. Sulphide ores are converted to metal oxides by roasting (heating in the presence of air). When zinc blende is heated in the presence of surplus air, it is converted into zinc oxide.

3. Gold.

Explanation:

Because gold is less reactive than silver. The other metals are more reactive than silver and can displace it from silver nitrate solution.

2. Electrical conductivity in solid state.

Explanation:

Because ionic compounds conduct electricity only in molten state or when dissolved in water to form aqueous solution.

2. Ag

Explanation:

Ag will be replaced from the solution of its salt by the other three metals.

3. Fe₂O₃ + Al.

Explanation:

In this thermite reaction, iron (III) oxide and aluminium powder are combined and heated. Iron oxide gets reduced to iron by the action of reducing agent aluminium and produces excess heat. The molten iron produced is poured in the middle of the broken pieces of irons that are fixed mutually.

4. CuSO₄ + Fe.

Explanation:

Iron (Fe) is a more reactive metal than copper, which can displace copper from copper sulphate.

4. Au and Ag.

Explanation:

Gold (Au) and silver (Ag) are highly non-reactive. Hence, they are available in native state in nature and do not react with oxygen or any other element in the atmosphere.

3. Bromine.

Explanation:

Bromine is the non-metal that is a liquid.

4. Iron.

Explanation:

Iron can be obtained from hematite ore. Hematite ore contains the compound iron (III) oxide (Fe₂O₃).

3. Na and Mg.

Explanation:

Sodium (Na) and magnesium (Mg) are highly reactive metals. They are not easily reduced by carbon and aluminium. Thus, they are extracted by electrolytic reduction or electrolysis of their molten chlorides (sodium chloride, NaCl, and magnesium chloride, MgCl₂).

4. Hg

Explanation:

Mercury (Hg) is the metal that exists in liquid state at room temperature.

2. Cinnabar.

Explanation:

Cinnabar is an important ore of mercury. Its compound is mercury (II) sulphide (HgS).

3. Haematite.

Explanation:

Haematite is an iron ore and the compound is iron (III) oxide (Fe₂O₃).

3. Ethyne.

Explanation:

An ethyne molecule (H - C ≡ C - H) contains a triple bond between two carbon atoms and two single bonds between carbon and hydrogen atoms.

4. Zinc amalgam.

Explanation:

Generally, alloys containing mercury as one of its constituents are known as amalgam. Zinc amalgam is an alloy of zinc and liquid mercury.

3. Steel.

Explanation:

Steel is an alloy that contains a non-metal carbon as one of its constituents. It consists of iron with carbon (0.1 to 1.5%).

4. Mercury and copper.

Explanation:

Both mercury and copper are less reactive metals and are placed low in the reactivity series. Hence, they can be extracted by heating their sulphides in air and further reducing their oxides by heating.

4. Magnesium and aluminium.

Explanation:

This is because magnesium and aluminium are highly reactive metals and are placed high in the reactivity series. This is also due to the fact that their oxides are very stable and cannot be reduced easily.

2. CCl₄

Explanation:

Because it is a covalent compound.

4. Lithium ion battery.

Explanation:

Because lithium ion is a good conductor of electricity.

4. Y³⁺

Explanation:

Number of protons is equal to number of electrons in an atom. Hence, electronic configuration of element Y is 2, 3. Thus, it becomes stabilised by donating its 3 electrons to form Y³⁺.

3. 10

Explanation:

Number of protons is equal to the number of electrons in an atom. It is given that one atom of an element X contains 8 electrons.

Therefore, number of electrons in its ion X²⁻ = 10 + 2 = 12

3. He

Explanation:

Atomic number of helium is 2. It contains 2 electrons in its atom.

4. Nitrogen and ethyne.

Explanation:

In a nitrogen molecule, each nitrogen atom shares its 3 electrons to form a triple bond among them. In an ethyne molecule, each carbon atom shares 3 electrons to form a triple bond among them.

3. Mercury.

Explanation:

An amalgam is an alloy of mercury with one or more metals. The combination of sodium with liquid mercury is called sodium amalgam. Amalgam of mercury with gold, silver or zinc is widely used for dental fillings.

4. Hg

Explanation:

Mercury is a low reactive metal. Thus, it can be extracted from its ore cinnabar, HgS, by heating it in air.

3. Al

Explanation:

Aluminium can be extracted from bauxite. Bauxite is an ore of aluminium and the compound is aluminium oxide (Al₂O₃.2H₂O).

2. Manganese.

Explanation:

Manganese is extracted from its oxide ore, pyrolusite. The name of the compound in the ore is manganese dioxide having chemical formula MnO₂.

4. Aluminium and zinc.

Explanation:

Both aluminium and zinc oxides react with acids and bases to form salt and water.

3. Bauxite.

Explanation:

Bauxite is one of the major ores of aluminium. Its compound is aluminium oxide (Al₂O₃.2H₂O).

2. Silver.

Explanation:

Because silver lies below other metals in the reactivity series.

1. Na and K.

Explanation:

Because Na and K are metals whose oxides are basic in nature, which can turn phenolphthalein solution pink.

4. Phosphorus and sulphur.

Explanation:

Phosphorus and sulphur are non-metals whose oxides are acidic in nature. These oxides turn blue litmus solution to red.

3. Potassium and magnesium.

Explanation:

Potassium and magnesium are metals whose oxides are basic in nature. These oxides turn red litmus solution to blue.

3. 8 or 2.

Explanation:

Helium is the only noble gas that has 2 electrons in its valence shell. Other noble gases have 8 electrons in their valence shells.

4. Y is a non-metal and Z is a metal.

Explanation:

Element Y has 1 less electron to complete its octet which is a property of non-metals. On the other hand, element ​Z has 2 extra electrons to become stabilised which is a property of metals.

3. P and S

Explanation:

Element P needs 4 electrons to complete its octet. They can be shared with element S, which needs only 1 electron to complete its octet.

4. B and D

Explanation:

Element B has the electronic configuration of 2, 6. It requires 2 electrons to complete its octet. On the other hand, element D has the electronic configuration of 2, 8, 2. It requires to release 2 electrons to complete its octet.

Thus, both atoms react to form ionic bonds by transfer of electrons.

2. 18

Explanation:

Anion Y⁻ has one more electron than its neutral atom. Y atom has 17 electrons and therefore, in Y⁻, number of electrons will be 18(17 + 1).

1. 18

Explanation:

Because X⁺ ion contains one less electron than X.

3. X²⁻

Explanation:

Element X needs 2 electrons to complete its octet. Therefore, it forms X²⁻ anion.

3. Sulphide.

Explanation:

Silver reacts with hydrogen sulphide gas in the air and forms a think black layer of silver sulphide (Ag₂S) on it. Silver jewellery or ornaments become dull because of the formation of silver sulphide coating on their surfaces.

2. Na.

Explanation:

Rock salt is a chloride ore of sodium. The name of the compound in the ore is sodium chloride with chemical formula NaCl.

2. Al₂O₃

Explanation:

Al₂O₃ can react with acids as well as bases to form salt and water.

2. HCl and CCl₄.

Explanation:

Both these compounds are formed by sharing of electrons and hence, they form covalent bonds and not ionic bonds.

4. Calcium.

Explanation:

Calcium lies above the other three metals in reactivity series.

4. Na₂O

Explanation:

Because Na₂O is a metal oxide that is basic in nature.

3. C₂H₄

Explanation:

An ethene molecule (C₂H₄) contains one double bond between two carbon atoms and four single bonds between carbon and hydrogen atoms.

4. Carbon tetrachloride.

Explanation:

It is a covalent compound.