The bond lengths of diatomic molecules of elements X, Y, and Z respectively are 143, 110, and 121 pm. The atomic numbers of X, Y, and Z respectively are:
1
2
3
4
Official Solution
Correct Option: (1)
- The bond length of a diatomic molecule depends on atomic size.
- Fluorine (F) has an atomic number 9 and forms a bond with a length of 143 pm.
- Nitrogen (N) has an atomic number 7 and forms a bond with a length of 110 pm.
- Oxygen (O) has an atomic number 8 and forms a bond with a length of 121 pm.
- Hence, the correct sequence of atomic numbers is .
Thus, the correct answer is:
02
PYQ 2024
hard
chemistryID: ap-eamce
Identify the set of molecules in which the central atom has only one lone pair of electrons in their valence shells:
1
BrF , SF , SnCl
2
BrF , XeF , SnCl
3
XeF , NH , ClF
4
XeF , ClF , SF
Official Solution
Correct Option: (1)
Step 1: Identify Lone Pairs in Given Molecules BrF : Br has 7 valence electrons, and after forming 5 bonds with F, it has one lone pair. SF : S has 6 valence electrons, forming 4 bonds with F and having one lone pair. SnCl : Sn has 4 valence electrons, forming 2 bonds with Cl and having one lone pair. Step 2: Verify Other Options XeF : Xe has two lone pairs. NH : N has one lone pair but is not included in the correct set. ClF : Cl has two lone pairs. XeF : Xe has no lone pairs. Thus, the correct set is BrF , SF , SnCl .
03
PYQ 2024
medium
chemistryID: ap-eamce
Hydrolysis of XeF gives HF, O , Xe and 'X'. The structure of 'X' is
1
pyramidal
2
Square pyramidal
3
octahedral
4
Square planar
Official Solution
Correct Option: (1)
The hydrolysis of XeF is given by the following reaction:
The 'X' in this reaction is XeO . To determine the structure of XeO , we need to find the number of electron pairs around the central atom Xe. Xe has 8 valence electrons. Each oxygen atom forms a double bond with Xe, using 2 electrons each. So, 3 oxygen atoms use 6 electrons. The remaining 2 electrons form a lone pair. Thus, there are 3 bond pairs and 1 lone pair, making a total of 4 electron pairs. According to VSEPR theory, the arrangement of electron pairs is tetrahedral. However, due to the presence of a lone pair, the shape of the molecule is pyramidal.
04
PYQ 2024
medium
chemistryID: ap-eamce
The correct formula used to determine the formal charge ( ) on an atom in the given Lewis structure of a molecule or ion is (V = number of valence electrons in free atom, U = number of unshared electrons on the atom, B = number of bonds around the atom)
1
2
3
4
Official Solution
Correct Option: (3)
The formal charge formula is: where:
- = Number of valence electrons in a free atom.
- = Number of unshared (lone pair) electrons.
- = Number of bonds formed by the atom.
This formula is used to determine the charge on atoms in Lewis structures to understand molecular stability.
Thus, the correct answer is:
05
PYQ 2024
medium
chemistryID: ap-eamce
In which of the following cases, there is no change in hybridization of the central atom?
1
2
3
4
Official Solution
Correct Option: (1)
Step 1: Understanding Hybridization Changes - has sp hybridization with a lone pair. - When it gains a proton to form , the lone pair is replaced by a bonding pair, but the hybridization remains sp . For the other cases: - (sp ) changes to (sp ). - (sp d) changes to (sp d ). - (sp d) changes to (sp d ). Thus, only in option (1), the hybridization remains unchanged.
06
PYQ 2024
medium
chemistryID: ap-eamce
In the given structure of Diborane, are respectively:
1
2
3
4
Official Solution
Correct Option: (3)
Step 1: Understanding Diborane Structure Diborane ( ) consists of two boron atoms bonded to four terminal hydrogen atoms and two bridging hydrogen atoms. The structure includes two types of bond angles: - The bridge hydrogen atoms form a bond angle ( ) of . - The terminal hydrogen atoms form a bond angle ( ) of . This occurs due to the presence of three-center two-electron bonds in the bridging hydrogens, causing bond angle distortions.
07
PYQ 2024
medium
chemistryID: ap-eamce
Match the following bond enthalpies with their respective bonds:
1
A-II, B-III, C-I, D-IV
2
A-II, B-IV, C-III, D-I
3
A-III, B-I, C-I, D-IV
4
A-III, B-I, C-IV, D-II
Official Solution
Correct Option: (1)
Step 1: Identifying bond enthalpies of the given bonds
- Silicon-Silicon ( ) bond enthalpy = 240 kJ/mol.
- Carbon-Carbon ( ) bond enthalpy = 348 kJ/mol.
- Tin-Tin ( ) bond enthalpy = 297 kJ/mol.
- Germanium-Germanium ( ) bond enthalpy = 260 kJ/mol. Step 2: Matching the correct bond enthalpies
Comparing with the given data:
Thus, the correct match is:
08
PYQ 2024
medium
chemistryID: ap-eamce
The bond order of which of the following two species is the same?
1
2
3
4
Official Solution
Correct Option: (2)
Step 1: Use the Bond Order Formula Bond order is given by: Step 2: Compute Bond Orders : Electronic configuration in molecular orbitals gives bond order = 2. : Electronic configuration in molecular orbitals also gives bond order = 2. Since both species have the same bond order, they are the correct answer.
09
PYQ 2024
easy
chemistryID: ap-eamce
Which of the following sets are correctly matched? (i) B2H6- electron deficient hydride (ii) NH3- electron precise hydride (iii) H2O- electron rich hydride
1
only
2
3
only
4
only
Official Solution
Correct Option: (1)
Step 1: Classification of Hydrides - Electron-deficient hydrides: (Diborane) lacks enough electrons for bonding, making it electron-deficient. - Electron-precise hydrides: is not electron-precise because it has a lone pair. - Electron-rich hydrides: has lone pairs and is electron-rich.
Thus, the correct matches are and .
10
PYQ 2024
medium
chemistryID: ap-eamce
The correct order of decomposition temperature of (X), (Y), (Z) is:
1
2
3
4
Official Solution
Correct Option: (1)
In general, the decomposition temperature of a metal carbonate increases with the size of the metal ion. The trend of decomposition temperature for carbonates is:
Thus, the correct order is:
11
PYQ 2024
medium
chemistryID: ap-eamce
The correct increasing order of number of lone pair of electrons on the central atom of , , and is
1
< < <
2
< < <
3
< < <
4
< < <
Official Solution
Correct Option: (2)
Step 1: has no lone pairs on the central atom. has two lone pairs, has one lone pair, and has three lone pairs.
Step 2: Therefore, the correct increasing order of lone pairs is <(SnCl_2\) < <(XeF_2\) .
12
PYQ 2024
medium
chemistryID: ap-eamce
Lithium forms an alloy with ‘X’. This alloy is used to make armor plates. What is ‘X’?
1
Mg
2
Pb
3
Al
4
Cr
Official Solution
Correct Option: (1)
Step 1: Understanding Lithium Alloys Lithium forms lightweight alloys that are used in aerospace and defense applications.
Step 2: Choosing the correct metal Among the given options, lithium forms an alloy with magnesium (Mg), which is used to make armor plates. Thus, the correct answer is Mg.
13
PYQ 2024
medium
chemistryID: ap-eamce
In which of the following sets of molecules, the central atoms of molecules have same hybridisation?
1
NH3,
2
H2O,
3
SF4, CH4
4
XeF6, IF7
Official Solution
Correct Option: (4)
Step 1: The hybridisation of central atoms in XeF6 and IF7 is sp3d2. Both have six electron pairs around the central atom.
Step 2: The other options have different hybridisations due to the number of bonding pairs and lone pairs on the central atom.
14
PYQ 2024
medium
chemistryID: ap-eamce
Which one of the following is used as piezoelectric material?
1
Tridymite
2
Quartz
3
Zeolite
4
Mica
Official Solution
Correct Option: (2)
Quartz is a widely used piezoelectric material because of its ability to generate an electric charge when subjected to mechanical stress. It is used in various electronic and mechanical applications, including oscillators and sensors.
15
PYQ 2024
medium
chemistryID: ap-eamce
Identify the correct sets: (i) Boron fibres- bulletproof vest (ii) Metal borides- protective shields (iii) Borax- glass wool
1
only
2
3
only
4
only
Official Solution
Correct Option: (2)
Step 1: Explanation of Each Set Boron fibers: Used in bulletproof vests due to their high strength. Metal borides: Used in protective shields because of their hardness and thermal stability. Borax: Used in the manufacturing of glass wool.
16
PYQ 2024
medium
chemistryID: ap-eamce
Which of the following is/are ionic in nature? (i) GeF4 (ii) SnF4
(iii) PbF4
1
only
2
only
3
only
4
only
Official Solution
Correct Option: (2)
Step 1: Nature of Bonding GeF : Covalent SnF and PbF : More ionic due to higher polarization and lower covalent character.
