Metals and Non-metals

Solution

Metals are known for their unique physical properties which include lustre, malleability, ductility, conductivity, and sonority. Lustre refers to the shiny appearance of metals when freshly cut or polished, e.g., gold and silver. Malleability is the ability of metals to be hammered into thin sheets, e.g., aluminium foils. Ductility allows metals to be drawn into wires, e.g., copper wires in electrical cables. Metals are good conductors of heat and electricity, with silver and copper being the best examples. Sonority is the property of producing a ringing sound when struck, e.g., school bells made of metals. These properties make metals indispensable in various applications, from construction to electronics.

Solution

Metals react with oxygen to form metal oxides, which are generally basic in nature. For example, magnesium burns in air to form magnesium oxide, a basic oxide. However, some metal oxides like aluminium oxide and zinc oxide are amphoteric, reacting with both acids and bases. The reaction of metals with oxygen varies; sodium and potassium react vigorously, while iron reacts slowly forming rust. The basic oxides turn red litmus blue, indicating their basic nature. These reactions are crucial in understanding the reactivity series of metals and their applications in daily life, such as in the prevention of corrosion.

Solution

Metals react with water to form metal hydroxides and hydrogen gas. The reactivity varies; potassium and sodium react violently with cold water, while calcium reacts less violently. Magnesium reacts with hot water, and metals like aluminium, iron, and zinc react with steam. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas, releasing heat. This reactivity is a key factor in the storage of metals like sodium in kerosene. The reactions demonstrate the position of metals in the reactivity series and their potential hazards and uses.

Solution

Electrolytic refining is used to purify metals like copper. In this process, the impure metal is made the anode, and a thin strip of pure metal is the cathode. The electrolyte is a solution of the metal salt. When electric current is passed, the anode dissolves, depositing pure metal on the cathode. Impurities settle as anode mud. For example, in copper refining, impure copper dissolves from the anode and pure copper deposits on the cathode. This method ensures high purity metals essential for electrical and electronic applications.

Solution

Metals occur in nature either in free state or as compounds. Less reactive metals like gold and silver are found free, while reactive metals are found as oxides, sulphides, or carbonates. The extraction process depends on the metal's reactivity. Metals low in the activity series are extracted by heating their oxides, those in the middle by reducing their oxides with carbon, and highly reactive metals by electrolysis. For example, iron is extracted from its oxide by reduction with carbon in a blast furnace, while aluminium is extracted from bauxite by electrolysis. These methods are vital for obtaining metals for various uses.

Solution

Alloys are homogeneous mixtures of two or more metals, or a metal and a non-metal, designed to enhance properties like strength, resistance to corrosion, and durability. For example, steel is an alloy of iron and carbon, making it stronger than pure iron. Brass, an alloy of copper and zinc, is used in musical instruments for its acoustic properties. Alloys like stainless steel (iron, chromium, nickel) resist rusting, making them ideal for utensils and medical instruments. The creation of alloys is a significant advancement in metallurgy, enabling the use of metals in diverse and challenging environments.

Solution

Corrosion is the deterioration of metals due to reactions with environmental substances like oxygen and moisture. For example, iron rusts when exposed to moist air, forming hydrated iron(III) oxide. Prevention methods include painting, oiling, galvanizing, and alloying. Galvanization coats iron with zinc to prevent rusting, even if the coating is damaged. Alloying, such as making stainless steel, also prevents corrosion. These methods are crucial in extending the life of metal structures and objects, saving costs and resources.

Solution

Non-metals exhibit chemical properties opposite to metals. They react with oxygen to form acidic or neutral oxides, e.g., sulphur forms sulphur dioxide, an acidic oxide. Non-metals gain electrons to form anions, e.g., chlorine forms chloride ions. They do not displace hydrogen from acids but react with hydrogen to form hydrides, e.g., ammonia (NH3). Non-metals are poor conductors of heat and electricity, except graphite. These properties determine their uses, such as sulphur in gunpowder and chlorine in water purification.

Solution

The reactivity series is a list of metals arranged in order of their decreasing reactivity. Potassium is the most reactive, and gold is the least. This series helps predict the outcome of reactions, such as displacement reactions where a more reactive metal displaces a less reactive one from its compound. For example, iron can displace copper from copper sulphate solution. The series also guides the extraction of metals and their storage methods, like keeping sodium in kerosene. Understanding the reactivity series is fundamental in chemistry for practical applications and safety measures.

Solution

Ionic compounds are formed by the transfer of electrons from metals to non-metals, resulting in oppositely charged ions held by electrostatic forces. For example, sodium chloride (NaCl) is formed when sodium loses an electron to chlorine. These compounds have high melting and boiling points, are soluble in water, and conduct electricity in molten or aqueous states due to free ions. They are brittle and solid at room temperature. Ionic compounds like NaCl are essential in daily life, from table salt to industrial applications.

Solution

Metals are lustrous, malleable, ductile, and good conductors of heat and electricity. Examples include iron, copper, and aluminium. Non-metals lack these properties; they are brittle, not malleable or ductile, and poor conductors. Examples include sulfur and oxygen. These properties dictate their uses, such as metals in construction and non-metals in insulation.

Solution

Metals react with oxygen to form oxides, with water to form hydroxides or oxides and hydrogen, and with acids to form salts and hydrogen. Reactivity varies: potassium reacts violently with water, while gold does not react. Examples: 4K + O2 → 2K2O; 2Na + 2H2O → 2NaOH + H2.

Solution

In electrolytic refining, impure copper is made the anode, pure copper the cathode, and copper sulfate solution the electrolyte. On passing current, copper from the anode dissolves and deposits on the cathode. Impurities settle as anode mud. This method ensures high purity.

Solution

Amphoteric oxides react with both acids and bases. Examples: Al2O3 and ZnO. Reactions: Al2O3 + 6HCl → 2AlCl3 + 3H2O; Al2O3 + 2NaOH → 2NaAlO2 + H2O.

Solution

The thermit reaction is highly exothermic, used to join railway tracks. Fe2O3 + 2Al → 2Fe + Al2O3 + heat. It's applied where high heat is needed to melt metals.

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The reactivity series lists metals in order of their reactivity. A more reactive metal can displace a less reactive one from its compound. Example: Zn + CuSO4 → ZnSO4 + Cu.

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Corrosion is the deterioration of metals due to reactions with environment. Rusting requires oxygen and water. Prevention methods: painting, galvanizing, alloying.

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Roasting heats sulfide ores in excess air to convert them to oxides, e.g., 2ZnS + 3O2 → 2ZnO + 2SO2. Calcination heats carbonate ores in limited air, e.g., ZnCO3 → ZnO + CO2. These processes make ores suitable for reduction.

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Alloys are harder, more durable, and resistant to corrosion than pure metals. Examples: stainless steel (utensils), 22 carat gold (jewelry).

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Sodium chloride forms when sodium loses an electron to chlorine, forming Na+ and Cl- ions, held by ionic bonds. Properties: high melting point, soluble in water, conducts electricity in molten state.

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Gold and silver are used for making jewelry due to their low reactivity, which prevents them from corroding or tarnishing easily. Their lustrous appearance and malleability allow them to be crafted into intricate designs. Additionally, their rarity adds to their value.

Solution

Electrolytic refining involves passing an electric current through a solution of copper sulfate with impure copper as the anode and pure copper as the cathode. Pure copper deposits on the cathode, while impurities settle as anode mud. This method is preferred because it produces high-purity copper suitable for electrical applications.

Solution

Metals are generally lustrous, malleable, ductile, and good conductors of heat and electricity, like copper and iron. Non-metals are usually dull, brittle, poor conductors, like sulfur and oxygen. However, exceptions like graphite (a non-metal) conduct electricity.

Solution

The thermit reaction, involving aluminum and iron oxide, produces molten iron and a large amount of heat, making it ideal for welding railway tracks. The high temperature ensures a strong weld, and the reaction's exothermic nature provides the necessary energy without external power sources.

Solution

Aluminum is more reactive than carbon, so it cannot be reduced by carbon. Electrolysis of molten aluminum oxide is used, which is energy-intensive, increasing costs but ensures high purity, essential for aluminum's applications in aerospace and packaging.

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Iron rusts in the presence of oxygen and water. Prevention methods include painting (for stationary objects), galvanizing (for outdoor structures), and alloying (for tools and utensils), each suited to the object's exposure to corrosive elements.

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Metal extraction can lead to habitat destruction, pollution, and high energy consumption. Sustainable practices include recycling metals, using bioleaching for extraction, and improving energy efficiency in smelting processes.

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Alloys like brass (copper and zinc) and bronze (copper and tin) are harder, more corrosion-resistant, and have lower melting points than pure metals, making them suitable for musical instruments, medals, and marine applications.

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Sodium chloride forms when sodium donates an electron to chlorine, creating ions that attract each other. Ionic compounds have high melting points and conduct electricity when molten, unlike covalent compounds like methane, which have low melting points and do not conduct electricity.

Solution

The reactivity series predicts that a more reactive metal can displace a less reactive one from its compound. For example, zinc can displace copper from copper sulfate, but copper cannot displace zinc from zinc sulfate, as zinc is more reactive than copper.