D Block Elements

Step 1: Recall that an Ellingham diagram is used in metallurgy to study the feasibility of reduction of metal oxides.
Step 2: It is a graphical representation of the variation of Gibbs free energy change ( ) with temperature.
Step 3: Since , the diagram plots on the y-axis against temperature on the x-axis.
Step 4: Therefore, the Ellingham diagram represents the change of with temperature.

Step 1: Recall the flame test colours of common elements.
Step 2: Barium (Ba) produces an apple green colour in the Bunsen flame.
Step 3: Check the other options:

Be — does not give a characteristic flame colour.
Ca — gives a brick red flame.
Sr — gives a crimson red flame.

Step 4: Therefore, the element that gives an apple green colour is Barium.

Step 1: Determine the number of lone pairs on Xe in each compound using VSEPR theory.
Step 2: XeO Xenon has 8 valence electrons. It forms 3 Xe–O bonds and has 1 lone pair. So, XeO has 1 lone pair on Xe.
Step 3: XeF Xenon forms 6 Xe–F bonds and has 1 lone pair. So, XeF also has 1 lone pair on Xe.
Step 4: Check the remaining compounds: XeF has 3 lone pairs. XeF has 2 lone pairs.
Step 5: Therefore, the pair having the same number of lone pairs is XeO and XeF .

Step 1: Recall the definition of the Bohr magneton ( ). It is the natural unit of magnetic moment for an electron.
Step 2: The Bohr magneton in S.I. units is given by:
Step 3: Its standard numerical value in S.I. units is:
Step 4: Among the given options, option (B) correctly represents the Bohr magneton in joule per tesla (J T ), which is the S.I. unit.

Step 1: Recall the meaning of electron affinity. Electron affinity is the energy released when an electron is added to a neutral gaseous atom.
Step 2: In halogens, electron affinity generally increases up the group due to decreasing atomic size.
Step 3: However, fluorine has slightly lower electron affinity than chlorine because of strong electron–electron repulsion in its very small 2p orbital.
Step 4: Therefore, the correct order of electron affinity among halogens is:
Step 5: Writing this in increasing order:
Step 6: Hence, the correct option is (D).

Step 1: Industrial methanol synthesis utilizes a mixed catalyst of chromium oxide promoted zinc oxide.
Step 2: Other options: - Fe – used in Haber process. - Al O – dehydrating catalyst. - V O – contact process.
Step 3: Therefore only (B) fits. Hence → (B).

Step 1: Quartz, mica and asbestos are silicate minerals.
Step 2: All silicate minerals are built from the tetrahedral unit in which one Si atom is bonded to four oxygen atoms in a tetrahedral geometry.
Step 3: These tetrahedra link by sharing corners to produce different structures: - Quartz – 3D network of shared SiO units. - Mica – sheet silicate of the same tetrahedral building blocks. - Asbestos – chain silicate again constructed from SiO .
Step 4: Therefore the fundamental unit common to all is SiO .

Step 1: Check each pair from industrial/organic chemistry: - (A) Wilkinson catalyst is indeed used for hydrogenation → true. - (B) Ziegler-Natta reagents used for polymerization → true. - (D) Nickel used as hydrogenation catalyst → true.
Step 2: Vanadium pentoxide is used in contact process for H SO , not in Haber process.
Step 3: Therefore statement (C) is wrongly matched. Hence → (C).

Step 1: A species with odd electron number (35) is unstable.
Step 2: Metal carbonyls stabilize by pairing electrons.
Step 3: Two possibilities: - Gain one electron → 36 e (closed shell). - Combine two molecules → dimer with metal–metal bond.
Step 4: Therefore both reduction and dimerization stabilize. Hence → (D).

Step 1: In froth flotation, an activator is the reagent that selectively makes ore particles hydrophobic.
Step 2: Xanthates form surface complexes with sulphide ores:
Step 3: Cyanides (KCN/NaCN) are depressants, not activators. Copper sulphate activates ZnS only in special cases, not general activator.
Step 4: The standard universal activator = sodium ethyl xanthate. Hence → (C).

Step 1: Recall the structure of the modern (long form) periodic table. The modern periodic table is arranged based on increasing atomic number. Step 2: Identify the number of periods. There are 7 horizontal rows called periods. Step 3: Identify the number of groups. There are 18 vertical columns called groups. Step 4: Match with the options. The correct description is: Final Answer:

Step 1: Recall the classification of fibres. Fibres are broadly classified into:

Natural fibres (obtained from plants or animals)
Synthetic fibres (man-made fibres)
Step 2: Analyze each option.

Angora: A natural fibre obtained from the hair of Angora rabbits — not synthetic
Rayon: Man-made fibre derived from cellulose — synthetic (semi-synthetic)
Nylon: Fully synthetic fibre
Polyester: Fully synthetic fibre
Step 3: Final conclusion. The fibre which is not synthetic is Angora.

Step 1: Recall the meaning of sublimation. Sublimation is the process in which a substance changes directly from the solid state to gaseous state without passing through the liquid state. Step 2: Analyze the given substances.

Table salt: Does not sublime
Sugar: Decomposes on heating, does not sublime
Iodine: Sublimes on heating — correct
Potassium iodide: Does not sublime
Step 3: Final conclusion. The substance that shows sublimation is iodine.

Step 1: Analyze statement (A). Atoms do not always combine to form molecules. Some atoms exist independently, such as noble gases (He, Ne, Ar). Hence, statement (A) is not correct. Step 2: Analyze statement (B). Atoms are the fundamental building blocks from which molecules and ions are formed. This statement is correct. Step 3: Analyze statement (C). An atom is electrically neutral because it contains equal numbers of protons and electrons. This statement is correct. Step 4: Analyze statement (D). Atoms combine in large numbers to form matter that we can see, feel, and touch. This statement is correct. Step 5: Final conclusion. The incorrect statement is .

Step 1: Recall the historical development of classification of elements. The earliest systematic attempt to classify elements was made in the 18th century. Step 2: Identify the correct scientist. Antoine Lavoisier (1789) classified known elements into:

Metals
Non-metals
Gases
Earths
This was the first known classification based on physical properties. Step 3: Analyze the other options.

(A) Mendeleev — periodic table based on atomic mass
(B) Lothar Meyer — periodicity based on atomic volumes
(D) Henry Moseley — modern periodic law based on atomic number
Step 4: Final conclusion. The early attempt to classify elements as metals and non-metals was made by Lavoisier.