Understanding Metals and Non-Metals – Maharashtra Board Class 10 Solutions for Science and Technology

Understanding Metals and Non-Metals  – Maharashtra Board Class 10 Solutions for Science and Technology (English Medium)

AlgebraGeometryScience & TechnologyHistoryGeography & EconomicsEnglish

Solution 1.1:

Aluminium

Solution 1.2:

Brass

Solution 1.3:

Cryolite (AlF₃, 3NaF) and fluorspar (CaF₂)

Solution 1.4:

Aluminium

Solution 1.5:

Bauxite (Al₂O₃.H₂O)

Solution 2:

• Characteristics which are relevant to metals:
  1. Ductile
  2. Conduct electricity
  3. (1, 2, 3) valence electrons
• Characteristics which are relevant to their compounds:
  1. Basic oxides
  2. Discharged at the cathode

Solution 3:

1. Metal as a sulphide:  FeS (iron sulphide)
2. Metal as a carbonate: CaCO₃ (calcium carbonate)
3. Metal as an oxide: Al₂O₃ (aluminium oxide)

Solution 4.1:

The naturally occurring compounds of metals along with other impurities are known as minerals.
Examples: Granite, talc

Solution 4.2:

Ores contain metal compounds with impurities such as soil, sand and rocky material. These impurities are called gangue.

Solution 4.3:

Minerals from which metals are expected profitably and conveniently are called ores.
Examples: Bauxite (Al₂O₃.H₂O), Cinnabar (HgS)

Solution 4.4:

The process used for the extraction of metals in their pure form from their ores is called metallurgy.

Solution 4.5:

The process of heating an ore to a high temperature in excess of air and converting it into its oxide is called roasting.
Example: ZnS (zinc blende) is roasted to get ZnO (zinc oxide).

Solution 5.1:

1. Sodium cannot be kept in the open as it reacts with oxygen in the air and catches fire.
2. It does not react with kerosene and sinks in it, so it does not come in contact with air.
3. Hence, to protect sodium and to prevent it from catching fire, sodium is stored under kerosene.

Solution 5.2:

1. Gold and silver both have natural lustre. They are malleable and ductile, so it is good for delicate designs in jewellery.
2. Gold and silver are noble metals. They are not affected by air, water and acids under normal conditions. Hence, gold and silver are used to make jewellery.

Solution 5.3:

1. Calcium reacts with water less vigorously, so the heat generated is not sufficient for hydrogen to catch fire.
2. Instead the bubbles of hydrogen gas formed stick to the surface of the metal making it lighter to float on the water. Hence, calcium floats on water during the reaction with water.

Solution 5.4:

1. Ionic compounds are solids and due to strong electrostatic attraction between oppositely charged ions, they are hard too.
2. To break the strong ionic bonds, a large amount of energy is required. Hence, ionic compounds have high melting and boiling points.

Solution 5.5:

1. Copper reacts with oxygen in the air to form black copper oxide. Copper oxide slowly reacts with CO₂ in the air which forms a green coat of copper carbonate.
2. Lime juice and tamarind contain acid. The green coating of basic copper carbonate which is present on the surface of a tarnished copper utensil dissolves in acid. Thus, it becomes shiny again.
3. Hence, tarnished copper utensils are cleaned with lime juice or tamarind.

Solution 6:

Copper is more reactive than silver. So, when a copper coin is dipped in a silver nitrate solution, copper displaces silver from it. Thus, liberated silver gets deposited on the copper coin.
Cu_(s) + 2AgNO_3(aq)→ Cu(NO₃)_2(aq) + 2Ag_(s)

Solution 7:

1. The metal is more reactive if the number of electrons in the outermost orbit is less. Metal A has 1 electron in the outermost orbit shell, while metal B has 2 electrons. Therefore, metal A is more reactive than metal B.
2. Metal A is sodium and metal B is calcium.
3. Reactions of Na and Ca with dil. HCl are

• 2Na + 2HCl →2NaCl_(aq) + H_2(g)
• Ca + 2HCl → CaCl₂ + H_2(g)

      4. In both reactions, hydrogen gas is liberated and the respective salts are formed.

Solution 8:

Reactions involved in obtaining zinc from zinc sulphide:
A: 2ZnS + 3O₂→ 2ZnO + 2SO₂
B: ZnO + C → Zn + CO

Solution 9:

2Al_(s) + 3H₂O → Al₂O_3(s) + 3H_2(g)

Solution 9.2:
2Cu₂S_(s) + 3O₂  2Cu₂O + 2SO_2(g)
2Cu₂O_(s) + Cu₂S_(s)  6Cu_(s) + SO_2(g)

Solution 9.3:

Fe₂O₃  + 2Al → 2Fe + Al₂O₃ + Heat

Solution 9.4:

Mg_(s) + 2H₂O → Mg(OH)_2(aq) + H_2(g)

Solution 9.5:

Al₂O₃ + 2NaOH →2NaAlO₂ + H₂O

Solution 10.1:

The process of concentration of bauxite is known as Bayer’s process.

Solution 10.2:

At the cathode: Al³ + 3e^–→ Al

Solution 10.3:

Function: Cryolite is added to the molten mixture of alumina to reduce the melting point.

The formula of cryolite is (Na₃AlF₆).

Solution 10.4:

2Al(OH)₃   Al₂O₃ + 3H₂O

Solution 10.5:

Solution 10.6:

During the electrolysis of alumina, oxygen liberated at the carbon anode reacts with it. So, the anode gets oxidised. Thus, it erodes continuously. Hence, it is necessary to replace the anodes from time to time.

Solution 10.7:

When aluminium ore is heated with a caustic soda solution under high pressure for 2 to 8 hours and at 140°C to 150°C, aluminium oxide from aluminium ore dissolves in caustic soda as it is amphoteric in nature and forms sodium aluminate.
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O.

Solution 11:

Two methods of preventing the rusting of iron:

1. By oiling, greasing or varnishing its surface.
2. Galvanisation, i.e. by coating the iron surface with a thin layer of zinc.

Solution 12:

A homogeneous mixture of two or more metals or a metal and a non-metal in a definite proportion is called an alloy.
Examples:
Brass: Copper (60-90%) and Zinc (40-10%)
Bronze: Copper (81-90%) and Tin (19-10%)

Solution 13:

Metals can be arranged in the decreasing order of chemical reactivity as
Na > Ca > Mg > Zn > Fe > Cu.

Solution 14:

1. Magnesium has atomic number 12, so its electronic configuration is 2, 8, 2.
2. It loses 2 electrons from its outermost shell M, and the L shell becomes its outermost shell with a stable octet.
3. Its atomic number is 17, so its electronic configuration is 2, 8, 7. Thus, the chlorine atom has 7 electrons in its outermost shell. It requires 1 electron to complete the octet.
4. Thus, magnesium loses two electrons and gets two unit positive charge, giving the magnesium cation (Mg⁺⁺). These are gained by two chlorine atoms, one each which gives two chloride ions with one unit negative charge each, i.e. 2 (Cl^–).

Magnesium and chloride ions with opposite charges get attracted to each other and form an ionic bond. Thus, the ionic compound magnesium chloride (MgCl₂) is formed.

Solution 15:

Element X is a metal because its oxide is basic in nature.
It is a metal like Na or K.
Sodium combines with oxygen and forms sodium oxide (Na₂O). When this oxide dissolves in water, it forms an alkali, sodium hydroxide (NaOH), which turns red litmus blue.
2Na + O₂→ Na₂O
Na₂O + H₂O → 2NaOH