Inorganic Chemistry

71. Which one of the following blocks of elements is called ‘Representativ

Which one of the following blocks of elements is called ‘Representative elements’?

[amp_mcq option1=”s-block elements only” option2=”f-block elements only” option3=”d-block elements only” option4=”p-block elements together with s-block elements” correct=”option4″]

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The s-block elements and the p-block elements together are called ‘Representative elements’ or ‘Main Group elements’.
Representative elements are those where the last electron enters either the s orbital or the p orbital of the outermost shell. They exhibit a wide range of chemical properties and their valencies are generally predictable based on their group number.
The d-block elements are known as Transition elements, and the f-block elements are known as Inner Transition elements (Lanthanides and Actinides). These elements generally have more complex electron configurations and chemical behaviors compared to the representative elements.

72. Who among the following scientists developed the Modern Periodic Table

Who among the following scientists developed the Modern Periodic Table ?

[amp_mcq option1=”Henry Moseley” option2=”Dmitri Ivanovich Mendeleev” option3=”John Alexander Newlands” option4=”Johann Döbereiner” correct=”option1″]

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Henry Moseley developed the Modern Periodic Table based on atomic number.
Moseley’s work in 1913 using X-ray spectroscopy showed that the atomic number (the number of protons in an atom’s nucleus) is a more fundamental property than atomic mass for organizing the elements. Arranging elements by increasing atomic number resolves anomalies present in Mendeleev’s table.
Dmitri Mendeleev is credited with creating the first widely accepted periodic table in 1869, which was arranged by increasing atomic mass and predicted the existence and properties of undiscovered elements. John Alexander Newlands proposed the Law of Octaves in 1865, arranging elements by atomic weight. Johann Döbereiner’s Law of Triads (1829) grouped elements with similar properties. While these scientists made important contributions, Moseley’s work led to the arrangement used in the modern periodic table.

73. The oxidation state and covalency of Al in [AlCl (H₂O)₅]²⁺ are

The oxidation state and covalency of Al in [AlCl (H₂O)₅]²⁺ are

[amp_mcq option1=”+ 3 and 3″ option2=”+ 3 and 6″ option3=”+ 2 and 6″ option4=”+ 2 and 1″ correct=”option2″]

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The complex is [AlCl (H₂O)₅]²⁺.
Let the oxidation state of Aluminum (Al) be x.
The charge of the chloride ligand (Cl⁻) is -1.
The charge of the water ligand (H₂O) is 0 (neutral molecule).
The overall charge of the complex ion is +2.
The sum of the oxidation states of the central metal ion and the charges of the ligands equals the overall charge of the complex:
x + (charge of Cl) + 5 * (charge of H₂O) = +2
x + (-1) + 5 * (0) = +2
x – 1 = +2
x = +3
So, the oxidation state of Al in [AlCl (H₂O)₅]²⁺ is +3.
The covalency of the central metal atom/ion in a coordination complex is equal to its coordination number, which is the total number of sigma bonds formed between the metal and the ligands. This is typically the number of ligands directly attached to the central metal.
In [AlCl (H₂O)₅]²⁺, the Al³⁺ ion is bonded to one Cl⁻ ligand and five H₂O ligands.
Total number of ligands attached = 1 + 5 = 6.
The coordination number of Al is 6.
Therefore, the covalency of Al in this complex is 6.
The oxidation state is +3 and the covalency is 6.
Oxidation state is the charge the central atom would have if all ligands were removed along with the electron pairs they donate. Covalency in coordination complexes is the number of coordinate bonds formed, equal to the coordination number.
Aluminum typically exhibits an oxidation state of +3. It is a common central metal in coordination chemistry, often forming complexes with a coordination number of 6, resulting in an octahedral geometry.

74. What is the number of moles of carbon in a sample containing 72.06 g o

What is the number of moles of carbon in a sample containing 72.06 g of carbon?

[amp_mcq option1=”4″ option2=”6″ option3=”2″ option4=”8″ correct=”option2″]

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To find the number of moles of a substance, you divide the mass of the substance by its molar mass. The molar mass of carbon (C) is approximately 12.01 g/mol. Given the mass of carbon as 72.06 g, the number of moles is calculated as:
Number of moles = Mass / Molar Mass = 72.06 g / 12.01 g/mol ≈ 6.00 moles.
– The number of moles relates mass to the number of particles (atoms or molecules).
– Molar mass is the mass of one mole of a substance.
– The atomic mass of Carbon (C) is the basis for its molar mass.
The unit “mole” is the SI unit for the amount of substance. One mole contains approximately 6.022 x 10^23 particles (Avogadro’s number). The atomic mass unit (amu) is defined such that the atomic mass of Carbon-12 is exactly 12 amu. The molar mass in grams per mole is numerically equal to the atomic mass in amu.

75. Which one of the following statements about the law of chemical combin

Which one of the following statements about the law of chemical combination is not correct?

[amp_mcq option1=”Equal volumes of all gases at the same temperature and pressure contain equal number of molecules.” option2=”If two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of other element, are not in any proportion.” option3=”Matter can neither be created nor destroyed.” option4=”A given compound always contains exactly the same proportion of elements by weight.” correct=”option2″]

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The correct answer is that statement B is not correct.
The Law of Chemical Combination includes fundamental principles like the Law of Conservation of Mass, Law of Definite Proportions, and Law of Multiple Proportions.
Statement A describes Avogadro’s Law, a key principle relating to gases in chemical reactions. Statement C is the Law of Conservation of Mass. Statement D is the Law of Definite Proportions (or Constant Composition). Statement B contradicts the Law of Multiple Proportions, which states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers. The statement B says they are “not in any proportion”, which is false.

76. What are the major raw materials used in the manufacture of cement?

What are the major raw materials used in the manufacture of cement?

[amp_mcq option1=”Limestone and clay” option2=”Al2O3 and limestone” option3=”Fe3O4 and clay” option4=”Clay and MgO” correct=”option1″]

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The correct answer is Limestone and clay.
Cement is manufactured by heating a mixture of calcareous materials (primarily calcium carbonate from limestone) and argillaceous materials (clay or shale containing silica, alumina, and iron oxide).
Limestone (providing CaO) and clay (providing SiO₂, Al₂O₃, Fe₂O₃) are the two main raw materials used in the production of Portland cement. They are mixed in specific proportions and heated in a kiln to produce cement clinker, which is then ground into the final product.

77. Match List-I with List-II and select the correct answer using the code

Match List-I with List-II and select the correct answer using the code given below the Lists :

List-I
(Compound)		List-II
(Use)
A. Bleaching powder1. Removal of permanent hardness of water
B. Baking soda2. Making toys
C. Washing soda3. Ingredient in antacids
D. Plaster of Paris4. Disinfecting drinking water

[amp_mcq option1=”A-2, B-3, C-1, D-4″ option2=”A-4, B-1, C-3, D-2″ option3=”A-2, B-1, C-3, D-4″ option4=”A-4, B-3, C-1, D-2″ correct=”option4″]

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The correct answer is A-4, B-3, C-1, D-2.
Matching the compounds with their common uses.
Bleaching powder (Calcium hypochlorite) is used as a disinfectant for water (A-4). Baking soda (Sodium bicarbonate) is an ingredient in antacids due to its alkaline nature (B-3). Washing soda (Sodium carbonate) is used to precipitate calcium and magnesium ions, thus removing permanent hardness of water (C-1). Plaster of Paris (Calcium sulfate hemihydrate) hardens upon mixing with water and is used for making casts, statues, and toys (D-2).

78. Which one of the following elements exhibits singular valency?

Which one of the following elements exhibits singular valency?

[amp_mcq option1=”Sulphur” option2=”Phosphorus” option3=”Sodium” option4=”Copper” correct=”option3″]

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The correct answer is Sodium.
Valency is the combining capacity of an element. Some elements have a fixed valency (singular), while others exhibit variable valency.
Sodium (Na) is an alkali metal (Group 1) and typically loses one electron to form a +1 ion, exhibiting a fixed valency of 1. Sulphur (S) can have valencies of 2, 4, 6. Phosphorus (P) can have valencies of 3, 5. Copper (Cu) is a transition metal and commonly exhibits valencies of 1 and 2. Thus, sodium is the element among the options that exhibits a singular valency.

79. Which one among the following statements is not true for glass ?

Which one among the following statements is not true for glass ?

[amp_mcq option1=”Sodium silicate is known as water glass.” option2=”Glass is also called super cooled liquid.” option3=”Crystallinity develops on cooling of the molten mass of the glass.” option4=”Coloured glasses can be made by adding different colouring materials.” correct=”option3″]

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Statement C, “Crystallinity develops on cooling of the molten mass of the glass,” is not true for glass.
Glass is defined as an amorphous solid. The process of glass formation (vitrification) involves cooling a molten material rapidly enough to prevent the atoms or molecules from arranging themselves into a regular, repeating crystalline structure. If crystallization occurs during cooling, the material becomes a crystalline solid, not glass.
Statement A is true: Sodium silicate solution (Na₂SiO₃) is widely known as water glass or liquid glass. Statement B is true: Glass is often described as a supercooled liquid because it lacks a long-range crystalline order, its structure resembles that of a liquid, although its viscosity is extremely high, giving it the mechanical properties of a solid. Statement D is true: Coloured glasses are made by adding small amounts of various metal oxides or other colouring agents to the glass composition before melting, which absorb or scatter specific wavelengths of light.

80. Which one among the following statements for the gases mentioned below

Which one among the following statements for the gases mentioned below is not correct ?

[amp_mcq option1=”Hydrogen has 3 isotopes.” option2=”Helium is a commonly used gas in electric bulbs.” option3=”Oxygen is used to burn fuel in rocket engines in spacecraft.” option4=”Nitrogen can be used in gaseous form to replace air in food packaging.” correct=”option2″]

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Statement B, “Helium is a commonly used gas in electric bulbs,” is not correct.
Standard incandescent electric bulbs commonly use inert gases like Argon or Nitrogen to reduce filament evaporation and blackening of the bulb. While Helium can be used in some specialized discharge lamps or gas mixtures, it is not the gas commonly found in typical household electric bulbs.
Statement A is correct: Hydrogen has three common isotopes: Protium (¹H), Deuterium (²H), and Tritium (³H). Statement C is correct: Oxygen (or an oxidizer like Liquid Oxygen, LOX) is essential for burning fuel in rocket engines through combustion. Statement D is correct: Nitrogen is an inert gas used in Modified Atmosphere Packaging (MAP) for food to displace oxygen, preventing oxidation and inhibiting the growth of aerobic bacteria, thus extending shelf life.
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