Question 1

In Haber process of production of ammonia Al _2 O _3 is used as

Accepted Answer

In the Haber process for the synthesis of ammonia, finely divided iron is used as the catalyst. To enhance the activity of the iron catalyst, small amounts of aluminum oxide ( Al _2 O _3) and potassium oxide ( K _2 O ) are added. Substances that increase the efficiency or activity of a catalyst are known as promoters. Therefore, Al _2 O _3 acts as a promoter. Answer: Promoter

Question 2

Which of the following is the correct decreasing order of bond dissociation enthalpy of halogens ?

Accepted Answer

The bond dissociation enthalpy of halogens generally decreases down the group as the atomic size increases, which leads to less effective overlap of orbitals. However, the bond dissociation enthalpy of F _2 is exceptionally lower than that of Cl _2 and Br _2. This is due to the very small size of the fluorine atom, which results in strong interelectronic repulsions between the non-bonding electrons (lone pairs) on the two closely spaced fluorine atoms. The experimental values of bond dissociatio

Question 3

Which among the following oxoacids of chlorine exhibits +3 oxidation state of chlorine?

Accepted Answer

Let the oxidation state of chlorine be x. In HClO : +1 + x - 2 = 0 x = +1 In HClO _2: +1 + x + 2(-2) = 0 x = +3 In HClO _3: +1 + x + 3(-2) = 0 x = +5 In HClO _4: +1 + x + 4(-2) = 0 x = +7 Chlorine exhibits a +3 oxidation state in HClO _2. Answer: HClO _2

Question 4

What is the oxidation state of chlorine in its weakest oxoacid?

Accepted Answer

The oxoacids of chlorine are HClO, HClO_2, HClO_3, and HClO_4. The acidic strength of oxoacids of a halogen increases with an increase in the oxidation number of the halogen atom. As the number of oxygen atoms increases, the electron density is pulled away from the O-H bond, making it easier to release an H^+ ion. The order of acidic strength is HClO Therefore, the weakest oxoacid of chlorine is hypochlorous acid, HClO. Let the oxidation state of chlorine in HClO be x. The typical oxidation stat

Question 5

Which of the following reactions exhibits the reducing property of ozone ?

Accepted Answer

In the reaction NO (g) + O _3 (g) NO _2 (g) + O _2 (g) , nitrogen is oxidized from +2 to +4. O _3 acts as an oxidizing agent. In the reaction 2 KI (aq) + H _2 O (l) + O _3 (g) 2 KOH (aq) + I _2 (g) + O _2 (g) , iodine is oxidized from -1 to 0. O _3 acts as an oxidizing agent. In the reaction PbS (s) + 4 O _3 (g) PbSO _4 (s) + 4 O _2 (g) , sulphur is oxidized from -2 to +6. O _3 acts as an oxidizing agent. In the reaction H _2 O _2 (l) + O _3 (g) H _2 O (l) + 2 O _2 (g) , both hydrogen peroxide a

Question 6

Which of the following noble gases exhibits higher oxidation states ?

Accepted Answer

As we move down the group of noble gases, the atomic size increases and the ionization enthalpy decreases. Xenon has a relatively low ionization enthalpy, which allows its valence electrons to be excited to empty d-orbitals. This enables Xenon to form compounds with highly electronegative elements like fluorine and oxygen. Xenon exhibits higher oxidation states such as +2, +4, +6, and +8 in compounds like XeF _2, XeF _4, XeF _6, XeO _3, and XeO _4. Neon and Argon do not form stable compounds, an

Question 7

Which from following compounds has lowest thermal stability?

Accepted Answer

The thermal stability of interhalogen compounds of the type XY with respect to disproportionation follows the order: ClF > ICl > IBr > BrCl > BrF Bromine monofluoride (BrF) is highly unstable and rapidly undergoes disproportionation at room temperature to form bromine trifluoride and bromine: 3BrF BrF_3 + Br_2 Because of its high tendency to decompose, BrF has the lowest thermal stability among the given options.

Question 8

Which from following catalysts is used in contact process of industrial production of sulfuric acid using SO _2 and O _2 (air).

Accepted Answer

The contact process is used for the industrial production of sulfuric acid. The key step in this process is the catalytic oxidation of sulfur dioxide ( SO _2) to sulfur trioxide ( SO _3) using oxygen ( O _2) from the air. The reaction is: 2 SO _2(g) + O _2(g) 2 SO _3(g) This reaction is catalyzed by platinised asbestos or vanadium pentoxide ( V _2 O _5). Among the given options, platinised asbestos is the correct catalyst. Finely divided Ni is used in the hydrogenation of oils. Co-Th is used in

Question 9

Identify weakest acid from following.

Accepted Answer

The given acids are oxoacids of chlorine. The chemical formulas and oxidation states of chlorine in these acids are: Hypochlorous acid: HClO (Oxidation state of Cl = +1) Chlorous acid: HClO_2 (Oxidation state of Cl = +3) Chloric acid: HClO_3 (Oxidation state of Cl = +5) Perchloric acid: HClO_4 (Oxidation state of Cl = +7) The acidic strength of oxoacids of the same halogen increases with an increase in the oxidation number of the halogen atom. This is because a higher oxidation state of the cent

Question 10

What is O-O bond length in ozone ?

Accepted Answer

Ozone (O_3) is a resonance hybrid of two equivalent structures. Due to resonance, both O-O bonds in the ozone molecule are identical. The O-O bond length is intermediate between a typical O-O single bond (148 pm) and an O=O double bond (121 pm). The experimentally determined O-O bond length in ozone is 128 pm. Answer: 128 pm

Question 11

Which of the following is the correct decreasing order of oxidizing power of perhalate ions?

Accepted Answer

The oxidizing power of perhalate ions depends on their standard reduction potentials. A higher positive standard reduction potential indicates a stronger oxidizing agent. The standard reduction potentials (E^ ) for the reduction of perhalate ions to halate ions in acidic medium are: E^ ( BrO _4^- / BrO _3^-) = +1.74 V E^ ( IO _4^- / IO _3^-) = +1.65 V E^ ( ClO _4^- / ClO _3^-) = +1.20 V Since the reduction potential is highest for BrO _4^- and lowest for ClO _4^-, the decreasing order of oxidizi

Question 12

In the Charring process, concentrated sulfuric acid reacts with sugar to give sugar charcoal. What is the role of conc. H _2 SO _4 in this reaction?

Accepted Answer

The reaction of concentrated sulfuric acid with sugar (sucrose) is known as the charring process. C _ 12 H _ 22 O _ 11 conc. H _2 SO _4 12 C + 11 H _2 O In this reaction, concentrated sulfuric acid removes water molecules from the sugar molecule, leaving behind a black mass of elemental carbon, which is called sugar charcoal. This demonstrates the strong affinity of concentrated sulfuric acid for water. Therefore, concentrated H _2 SO _4 acts as a strong dehydrating agent. Answer: A dehydrating

Question 13

Match the Xenon compounds in Column-1 with its structure in Column-II. Column – I Column – II (a) XeF _4 (i) pyramidal (b) XeF _6 (ii) square planar (c) XeOF _4 (iii) distorted octahedral (d) XeO _3 (

Accepted Answer

For XeF _4: Xenon has 8 valence electrons. It forms 4 single bonds with fluorine atoms and has 2 lone pairs. The hybridization is sp^3d^2 and the shape is square planar. Thus, (a) matches (ii). For XeF _6: Xenon forms 6 single bonds with fluorine atoms and has 1 lone pair. The hybridization is sp^3d^3 and the shape is distorted octahedral. Thus, (b) matches (iii). For XeOF _4: Xenon forms 4 single bonds with fluorine atoms, 1 double bond with oxygen, and has 1 lone pair. The hybridization is sp^

Question 14

Which of the following is not characteristics of interhalogen compounds?

Accepted Answer

Interhalogen compounds are formed by the combination of two different halogens. They are covalent in nature due to the small electronegativity difference between the halogen atoms. They are generally volatile solids or liquids (except ClF, which is a gas) and are not explosive. They are highly reactive and form addition products with unsaturated hydrocarbons. Because halogens are highly electronegative, interhalogen compounds have a strong tendency to accept electrons. Therefore, they act as str

p Block Elements (Group 15, 16, 17 & 18) — Previous Year Questions & Solutions