Metals And Non-metals

When calcium reacts with water, it forms hydrogen gas (H₂). The reaction is given below:

Ca + 2H₂O → Ca(OH)₂ + H₂

The bubbles of hydrogen gas produced in the reaction gets stick to the surface of the metal. Hence, calcium floats on water.

Properties of gold and silver:

i. The outermost shell of gold and silver is completely filled. Therefore, they are chemically unreactive. Neither they react with water nor air, hence, they both are called as noble metals.

ii. They both have a metallic lustre too. The lustre remains for a very long time. It does not get fade away.

A is a non-metal

Explanation:

Oxides of non-metals → acidic in nature

Oxides of metals → basic in nature

Hence, element which forms an oxide A₂O₃ which is acidic in nature is a non-metal.

Electrolytic reduction is a method by which metals of high reactivity are purified.

Explanation: The metals which are at the top of the reactivity series are very reactive.

The reactive metals cannot be obtained by simply heating with carbon. Because carbon being less reactive is not able to reduce the metals. Hence, these metals are obtained by electrolytic reduction.

X is carbon, Y is diamond and Z is graphite.

Explanation: Carbon (X) is a non-metal that can exist in different forms. Each form is called allotrope.

i. Diamond(Y) is the hardest natural substance. It is an allotrope of carbon

ii. Graphite (Z) is a good conductor of electricity. It is an another allotrope of carbon.

Note: Fullerene is also an allotrope of carbon.

Roasting is the process by which sulphide ores are concentrated. The sulphides ores are changed into oxides by heating them strongly in the presence of excess air. This process is known as roasting. The reaction is given below:

2ZnS + 3O₂ + heat → 2ZnO + 2SO₂

The insoluble impurities settle down at the bottom of the anode (the positively charged electrode) are known as anode mud.

(a) If sodium metal is kept in the open, it reacts vigorously with air and produces harmful effects. Hence to avoid such effects and to prevent accidental fires, they are kept immersed in kerosene.

(b) When alumninium powder is added in a copper sulphate solution, the blue colour of the solution goes away. The solution become colourless. Here, the displacement reaction is taking place. Aluminium being more reactive displaces copper from its own sulphate. As a result, aluminium sulphate is formed. The reaction is:

CuSO₄ + Al → Al₂(SO₄)₃ + Cu

Y is a non-metal. X and Z are metals.

Explanation: Y is non-metal because it has 7 valence electrons. It can gain one electron to achieve stable electronic configuration.

X (2,8) and Z (2,8,2) are metals because their outermost shells are completely filled.

The constituents of solder alloy are tin(60%) and lead(40%). The properties of solder which makes it suitable for welding electrical wires are:

i. The melting point of solder alloy is very low. This makes easy for solder alloy to melt very easily for welding.

ii. The electricity conductivity of solder alloy is very high. This makes possible for solder alloy to pass through it very easily.

The reaction of iron oxide, Fe₂O₃ with aluminium (Al) is highly exothermic reaction and is used to join broken railway tracks or cracked machine parts. Hence, the metal ‘X’ is Al.

The reaction is given below:

Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + Heat

The above reaction is known as the thermit reaction.

a) When zinc pieces are put into copper sulphate solution, the solution becomes colourless. The displacement reaction takes place. Zinc being more reactive than copper displaces it from its sulphate and as a result, zinc sulphate is formed. The reaction is:

Zn + CuSO₄→ ZnSO₄ + Cu

b) When silver pieces are put into green coloured ferrous sulphate solution, the solution will become pale white. The displacement reaction is taking place here. Silver being more reactive displaces the iron from its sulphate and as a result, silver sulphate is formed. The reaction is:

Ag + FeSO₄→ AgSO₄ + Fe

(a) Mg and N₂: Mg₃N₂ (magnesium nitride)

(b) Li and O₂: LiO₂ (lithium oxide)

(c) Al and Cl₂: Al₂Cl₃ (Aluminium chloride)

(d) K and O₂: K₂O (Potassium oxide)

(a) Almost all metals combine with oxygen present in air to form metal oxides:

Metal + Oxygen → Metal oxide

When magnesium (a metal) ribbon is burnt in the presence of air, it reacts with oxygen to form magnesium oxide (MgO₂), the following reaction takes place:

2Mg + O₂→ 2MgO₂

(b) Sodium metal reacts violently with water. The reaction is so violent and exothermic that the evolved hydrogen immediately catches fire. The reaction is:

2Na + H₂O → 2NaOH + H₂ + heat energy

(c) Aluminium do not react either with cold or hot water. It reacts with steam to form the aluminium oxide (Al₂O₃) and hydrogen. The reaction is:

2Al + 3H₂O → Al₂O₃ + 3H₂

Iodine is a non-metal which is lustrous.

Mercury is a metal which is liquid at room temperature.

It is given that compound ‘X’ conducts electricity and is soluble in water. These are the properties of an ionic compound. Hence, the given compound ‘X’ is an ionic compound.

The other two properties of ionic compounds are:

i. Physical nature: Ionic compounds are solid and hard because of the strong force of attraction between the positive and negative ions. These are brittle and can break into pieces if pressure is applied.

ii. Melting and boiling point: Ionic compounds have high melting and melting point.

It is given that an alkali metal A gives a compound B whose molecular mass is 40. The molecular mass of NaOH is 40:

23 × 1 + 16 + 1 = 40

The alkali metal is Na (A). When Na reacts with water, it forms NaOH (B). The reaction is:

When sodium hydroxide (B) reacts with aluminum oxide, it gives sodium alumninate (NaAlO₂). Hence, compound C is sodium alumninate. The reaction is:

The processof electrolytic refining of copper:

i. In this electrolytic refining, the electrolyte is a solution of copper sulphate.

ii. In this process, the anode is impure copper, whereas the cathode is a thin strip of pure copper.

iii. On passing the current through the electrolyte, the pure copper from the anode dissolves into the electrolyte.

iv. An equivalent amount of pure copper from the electrolyte is deposited at the cathode.

v. The insoluble impurities settle down at the bottom of the anode (the positively charged electrode) are known as anode mud.

When copper reacts with the moist CO₂ present in the air, it will loose its shiny brown surface and green coating will be formed on the surface of the copper. This green coating is of CuCO₃ and Cu(OH)₂. The reaction is:

2Cu + CO₂ + H₂O + O₂→ CuCO₃ and Cu(OH)₂.

i. The electronic configuration of a magnesium atom is 2, 8, 2. Hence, Mg will loose its two valence electrons to complete its octet. This results in the formation of Mg²⁺ion.

ii. The electronic configuration of a chlorine atom is 2, 8, 7. Hence, Cl will gain one electron to complete its octet. This results in the formation of Cl^- ion.

iii. Mg²⁺ is donating 2 electrons to each chlorine atoms (two chlorine atoms)

iv. As you can see that in the formation of the bond, the ions (Mg²⁺ and Cl^-) are involved Hence, the type of bond is an ionic bond.

Properties of magnesium chloride (MgCl₂):

i. It is water soluble.

ii. It is a good conductor of electricity.

iii. It has a high melting and boiling point.

iv. It is generally brittle.

a. Formation of oxide:

When copper is heated in air, it combines with oxygen to form copper oxide, black oxide. The reaction is:

Formation of hydroxide:

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalies (hydroxides). When sodium oxide dissolved in water, it produces NaOH (sodium hydroxide). The reaction is:

Na₂O + H₂O → 2NaOH

When metallic oxide reacts with both acids as well as bases are known as amphoteric oxides. For ex-

2Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O

i. Cold water:

Sodium metal reacts violently with water. The reaction is so violent and exothermic that the evolved hydrogen immediately catches fire. The reaction is:

2Na + H₂O → 2NaOH + H₂ + heat energy

ii. Hot water:

Magnesium reacts with hot water to form magnesium hydroxide and hydrogen. The reaction is:

Mg + 2H₂O → Mg(OH)₂ + H₂

iii. Steam:

Aluminium does not react either with cold or hot water. It reacts with steam to form the aluminium oxide (Al₂O₃) and hydrogen. The reaction is:

2Al + 3H₂O → Al₂O₃ + 3H₂

Metals such as lead, copper, silver, and gold do not react with water at all.

a. Roasting:

Roasting is the process by which sulphide ores are concentrated. The sulphides ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting. The reaction is given below:

2ZnS + 3O₂ + Heat → 2ZnO + 2SO₂

b. Calcination:

The carbonates ores are changed into oxides by heating strongly in the presence of excess air. This process is known as calcination. The reaction is given below:

ZnCO₃ + Heat → ZnO + 2CO₂

c. Electrolytic refining:

Many metals such as copper, zinc, silver, gold, copper are refined electrolytically. For example:

At cathode: Cu²⁺ + 2e^-→ Cu

At anode: Cu → Cu²⁺ + 2e^-

Steps involved in the extraction of metals of low and medium reactivity:

i. Metals low in the reactivity series are very unreactive. The oxides of these metals can be reduced to metals by heating alone.

ii. For ex- Cinnabar (HgS) is an ore of mercury.

iii. When cinnabar is heated in air, it is first converted into mercuric oxide (HgO). The reaction is:

2HgS + 3O₂ + heat → 2HgO + 2SO₂

iv. Mercuric oxide is then reduced to mercury on further heating. The reaction is:

2HgO + heat → 2Hg + O₂