Chapter 3 – Metals and Non-metals

Explanation:

(i) Mercury (Hg) is a metal that is a liquid at room temperature.

(ii) Sodium (Na) is a metal that is soft and can be easily cut with a knife.

(iii) Silver (Ag) is the best conductor of heat among metals.

(iv) Lead (Pb) is a poor conductor of heat.

Explanation:

1. The term "malleable" generally refers to something that can be easily shaped, molded, or bent without breaking or losing its integrity.

2. The term "ductile" refers to the ability of a material to be drawn, stretched, or deformed under tension without breaking or fracturing.

Explanation:

Sodium is a highly reactive metal. If left open, it will react with oxygen, allowing it to explore and catch fire. To inhibit reactions with oxygen, moisture, and carbon dioxide in the air, sodium metal is soaked in kerosene.

Explanation:

(i) Steam and iron react, releasing H2 and creating a magnetic oxide of iron.

3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

(ii) Calcium hydroxide and hydrogen are produced when calcium reacts with water.

Ca(s) + 2H2O(I) → Ca(OH)2(aq) + H2(g)

Potassium reacts aggressively and quickly with cold water, generating H2 that ignites.

2K(s) + 2H2O(I) → 2KOH(aq) + 2H2(g)

Explanation:

(i) Since it combines with iron (II) sulphate to create displacement, metal B is the most reactive.

(ii) When essence B is added to copper ( II) sulphate result, a  relegation response occurs, causing the blue colour of the copper ( II) sulphate result to fade and a red-brown copper deposit to develop on essence B. 

(iii)The most reactive metal is metal B, which displaces iron from its salt solution. Since it displaces copper from its salt solution, Metal A is less reactive. Metal C is even less reactive since it can only remove silver from its salt solution, while metal D is the least reactive because it cannot remove any metal from its salt solution. As a result, the metals' decreasing reactivity is B > A > C > D.

Explanation:

When diluted HCl is added to a reactive metal, hydrogen gas is released.

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)

Explanation:

Compared to iron, zinc is more electropositive and reactive. As a result, Zinc takes the place of Iron in its salt solution. The color of ferrous sulphate is a light green that eventually becomes colorless.

FeSO4 + Zn → ZnSO4 + Fe(s)

Light green Zinc sulphate(Colourless)

Explanation:

(i) Sodium: 

Oxygen:

(ii) Formation of Magnesium oxide:

When magnesium and oxygen react, an oxygen atom receives the two outermost electrons from the magnesium atom. An oxide ion (O2-) is created when an oxygen atom gains two electrons and an oxide ion (Mg2+) is created when two magnesium atoms lose two electrons.

Mg:  +

→ MgO

Formation of Sodium oxide:

An oxygen atom receives the two outermost electrons from two sodium atoms. The two sodium atoms combine to form sodium ions (2Na+) by giving up two electrons. The oxygen atom also produces an oxide ion (O2-) by gaining two electrons.

(iii) Sodium ions (2Na+) and oxide ions are found in sodium oxide complex (Na2O) (O2-).

Magnesium oxide compound (MgO) contains magnesium ions Mg2+ and oxide ions (O2-).

Explanation:

Ionic compounds have high melting points because of the strong electrostatic forces of attraction that exist between the oppositely charged ions in the crystal lattice structure. These electrostatic forces, also known as ionic bonds, are the result of the transfer of electrons from one atom to another, resulting in the formation of positively charged cations and negatively charged anions.

Because the ionic bond is very strong, a large amount of energy is required to overcome this attraction and separate the ions from each other. This energy is supplied in the form of heat, and the temperature required to overcome the electrostatic forces and melt the ionic compound is called the melting point.

Explanation:

(i) Minerals are naturally occurring substances (also known as elements) in the earth's crust. For example Alums, K2SO4. Al2(SO4)3.24H2O.

(ii) An ore is a natural material that contains a high enough concentration of one or more minerals to make it economically viable to extract and process. Ores are typically formed through geological processes such as volcanic activity, weathering, or sedimentation, and are found in various geological formations, including veins, deposits, and sedimentary layers.

(iii) Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue. The impurities must be removed from the ore prior to the extraction of the metal. The processes used for removing the gangue from the ore are based on the differences between the physical or chemical properties of the gangue and the ore. Different separation techniques are accordingly employed.

Explanation:

Gold (Au) and Silver (Ag) are two metals that are found in nature in the free state, meaning they occur in pure form without being chemically combined with other elements. They are both relatively unreactive and can be found in veins or nuggets in rocks and soil.

Explanation:

Metal is extracted from its oxide via the reduction technique. For example, heating zinc oxide with carbon reduces it to metallic zinc.

ZnO + C → Zn + CO

Ex: Lead oxide is reduced to lead by heating with carbon

PbO +C → Pb + CO

Explanation: 

A more reactive metal can push a less reactive metal out of its oxide. Among the metals zinc, magnesium, and copper, magnesium is the most reactive, copper is the least reactive, and zinc is the least reactive. The displacement response will occur in the following scenarios:

Explanation: 

Some metals are more resistant to corrosion than others due to their physical and chemical properties. Generally, metals that have a high resistance to corrosion are referred to as "noble metals". The most commonly known noble metals are:

1. Gold (Au)

2. Platinum (Pt)

3. Palladium (Pd)

4. Rhodium (Rh)

5. Ruthenium (Ru)

These metals are highly resistant to corrosion and oxidation, even at high temperatures and in harsh environments. They are commonly used in industrial applications where resistance to corrosion and oxidation is essential, such as in the production of electronic components, catalytic converters, and jewelry.

Explanation: 

An alloy is a mixture of two or more metals, or a metal and a non-metal, that are melted together and then cooled to form a solid material with specific properties. Alloys are formed by combining different metals in varying proportions to achieve specific characteristics such as increased strength, durability, or resistance to corrosion.

Explanation: 

The pair that will give displacement reactions is option (d) AgNO3 solution and copper metal.

A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its compound. In this case, copper is less reactive than silver and therefore cannot displace it from FeSO4 or NaCl solution. Similarly, aluminum is more reactive than magnesium, so it cannot displace magnesium from MgCl2 solution.

However, in option (d), copper is more reactive than silver, so it can displace silver from the AgNO3 solution. The reaction is as follows:

Cu (s) + 2AgNO3 (aq) → Cu(NO3)2 (aq) + 2Ag (s)

So, option (d) is the correct answer.

Explanation: 

The correct answer is (c) Applying a coat of zinc. Because adding grease and painting iron prevents corrosion, we cannot use these measures on a frying pan. As a result, putting a layer of zinc is the best way to keep an iron pan from rusting.

Explanation: 

Option (a) Calcium is the correct answer.

Calcium oxide is formed when calcium combines with oxygen. Calcium Hydroxide is formed when calcium oxide dissolves in water.

Carbon reacts with oxygen to generate carbon oxide, which is gas, hence option B is incorrect.

Silicon dioxide is formed when silicon combines with oxygen. This substance is insoluble in water. As a result, option C is incorrect.

The iron dioxide is formed when iron combines with oxygen. This substance is insoluble in water. As a result, option D is incorrect.

Explanation: 

The correct option is (c) Zinc is more reactive than tin.

Food cans are coated with tin, which is a non-reactive metal that does not react with the food contents and does not affect the taste or quality of the food. Tin is also resistant to corrosion and oxidation, which makes it an ideal material for food can coatings.

Zinc, on the other hand, is a more reactive metal than tin and would react with the acidic content of many foods, leading to discoloration, off-flavors, and even corrosion of the can. Zinc is also more susceptible to oxidation than tin, which can lead to the formation of a layer of rust on the surface of the can.

Therefore, tin is preferred over zinc as a coating material for food cans because of its non-reactivity and resistance to corrosion.

Explanation: 

(a) To distinguish between samples of metals and non-metals using the given materials:

1. Connect the battery, switch, and wires in a circuit.

2. Connect the bulb to the circuit so that it lights up when the circuit is closed.

3. Take a sample of the material to be tested and touch it to the wires on either side of the switch, so that it completes the circuit.

4. Close the switch and observe the behavior of the bulb.

Metals are good conductors of electricity, while non-metals are poor conductors. When a metal sample is connected to the circuit, it will allow the flow of electric current, completing the circuit and causing the bulb to light up. Non-metals, on the other hand, will not allow the flow of electric current, so the bulb will not light up.

(b) The method described above can be useful in distinguishing between metals and non-metals, but it has some limitations. For example, some non-metals, such as graphite and some forms of carbon, can conduct electricity and would therefore be incorrectly identified as metals using this method. Additionally, the test does not provide any information about the specific properties of the metal or non-metal being tested, so it may not be useful in identifying specific types of metals or non-metals.

Explanation: 

Amphoteric oxides are oxides that can act as both acidic and basic. In other words, they can react with both acids and bases to form salt and water. The ability of an oxide to act as an acid or a base depends on the nature of the other reactant.

Some examples of amphoteric oxides are:

1. Aluminum oxide (Al2O3): It reacts with both acids and bases to form salts and water. For example, with a strong acid such as hydrochloric acid (HCl), acts as a base and forms aluminum chloride (AlCl3) and water. With a strong base such as sodium hydroxide (NaOH), it acts as an acid and forms sodium aluminate (NaAlO2) and water.

2. Zinc oxide (ZnO): It also exhibits amphoteric properties and reacts with both acids and bases. For example, with a strong acid such as hydrochloric acid (HCl), acts as a base and forms zinc chloride (ZnCl2) and water. With a strong base such as sodium hydroxide (NaOH), it acts as an acid and forms sodium zincate (Na2ZnO2) and water.

Amphoteric oxides are important in various industrial applications, such as in the production of ceramics, catalysts, and semiconductors.

Explanation: 

Since they are highly reactive metals, zinc (Zn) and magnesium (Mg) will displace hydrogen from dilute acids. Since gold (Au) and silver (Ag) are less reactive, they will not replace hydrogen from dilute acids.

Explanation: 

In the electrolytic refining of a metal M, the anode, cathode, and electrolyte would depend on the specific metal being refined. However, in general, the following components are typically used:

Anode: The anode is typically made of the impure metal that is being refined. As an electric current is passed through the electrolyte, the metal at the anode is oxidized and dissolves into the electrolyte solution as metal ions.

Cathode: The cathode is typically made of pure metal or inert material, such as platinum or graphite. As electric current is passed through the electrolyte, metal ions from the solution are reduced at the cathode, forming a pure metal coating on the cathode.

Electrolyte: The electrolyte is typically a solution of a salt of the metal being refined, such as copper sulfate for the refining of copper. The electrolyte serves as a medium for the flow of electric current between the anode and cathode.

Explanation: 

(a) Sulphur dioxide is generated when sulphur powder is burned in the air.

(i) Sulphur dioxide has no impact on dry litmus paper.

(ii) Sulphur dioxide causes damp litmus paper to glow red as SO2 reacts with water to form sulphurous acid.

(b) S(s) + O2(g) → SO2(g)

SO2(g) + H2O →H2SO3

Explanation:

1. Rust-resistant paints can be used to cover the surface of iron to keep it from rusting.

2. Applying oil/grease to the surface of iron items prevents the iron surface from coming into touch with damp air.

Explanation: 

When non-metals combine with oxygen, they generally form acidic oxides, also known as non-metal oxides. These oxides are characterized by their ability to react with water to form acidic solutions.

Examples of non-metal oxides include:

• Carbon dioxide (CO2) is formed when carbon combines with oxygen

• Sulfur dioxide (SO2) formed when sulfur combines with oxygen

• Nitrogen dioxide (NO2) formed when nitrogen combines with oxygen

• Phosphorus pentoxide (P2O5) is formed when phosphorus combines with oxygen.

These oxides are usually molecular compounds, meaning they are made up of discrete molecules rather than an extended lattice structure like ionic compounds.

Explanation:

(a) Since platinum, gold, and silver are non-reactive metals, they are utilised to produce the jewellery. As a result, they are unaffected by air, water, or most chemicals. These metals have a high sheen and are malleable and ductile in nature, as well as having good corrosion resistance.

(b) Sodium, potassium, and lithium rapidly react with water, generating a large amount of heat. As a result, the hydrogen produced in the process causes a fire. When exposed to water, they react with moisture (water droplets) in the atmosphere to avoid contact with water. As a result, these metals are kept beneath oil.

(c) Aluminium creates a nonreactive surface of aluminium oxide on its surface. This type of coating inhibits other chemicals from interacting with aluminium. As a result, aluminium is utilised to make cooking utensils.

(d) It is simple to convert metal oxide into free metal. Furthermore, because metals are simpler to acquire directly from oxides than from carbonates or sulphides, carbonate and sulphide ores are first converted to oxides before the metals are extracted.

Explanation: 

Lemon or tamarind is used to clean tarnished copper vessels because its acids dissolve the layer of copper oxide or basic copper carbonate that is found on the surface of tarnished copper vessels. This restores their red-brown radiance. As a result, they are extremely good at cleaning tarnished copper vessels.

Explanation:

Explanation:

The goldsmith utilized a solution known as Aqua regia, which translates to "royal water" in Latin. It is a 3:1 blend of concentrated hydrochloric acid and concentrated nitric acid. Aqua regia has the ability to dissolve precious metals such as gold and platinum. They lose weight as the overlying layer of dull gold decoration is destroyed.

Explanation: 

Copper is used to produce hot water tanks rather than steel (an iron alloy) since copper does not react with water or steam, whereas iron interacts with steam to corrode the tank.