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All questions of Molecular Geometry for EmSAT Achieve Exam

Hybridisation of Acetylene is
  • a)
    sp
  • b)
    sp2
  • c)
    sp3
  • d)
    dsp2
Correct answer is option 'A'. Can you explain this answer?

Riya Banerjee answered
Since acetylene is made up of triple bond. So the hybridization of carbon in acetylene is sp.

Which of the following is nonpolar but contains polar bonds?
  • a)
    HCI
  • b)
    CO2
  • c)
    NH3
  • d)
    NO2
Correct answer is option 'A'. Can you explain this answer?

Pooja Mehta answered
This is why molecules like carbon dioxide are nonpolar despite having the polar carbon oxygen bonds. Molecules that contain non-polar bonds are not polar unless the central atom has one or more nonbonded pairs of electrons.

Valence Bond Theory was developed in the year
  • a)
    1916
  • b)
    1927
  • c)
    1930
  • d)
    1932
Correct answer is option 'B'. Can you explain this answer?

Krishna Iyer answered
The valence bond (VB) theory of bonding was mainly developed by Walter Heitler and Fritz London in 1927, and later modified by Linus Pauling to take bond direction into account. The VB approach concentrates on forming bonds in localized orbitals between pairs of atoms, and hence retains the simple idea of Lewis structures and electron pairs. 

 Which molecule has a trigonal pyramidal shape?
  • a)
    AB4E
  • b)
    AB2E2
  • c)
    AB3E
  • d)
    AB2E
Correct answer is option 'C'. Can you explain this answer?

Geetika Shah answered
AB3E: trigonal pyramidal (central atom + 3 outer atoms make a pyramid)
→ start with AB4 molecule (tetrahedral) and replace a B atom w/ lone pair
→ lone pair electrons push bonding electrons away
→ bond angles are now less than 109.5°

Which of the following molecule doesn’t have a lone pair?
  • a)
    BeCl2
  • b)
    XeF4
  • c)
    NH3
  • d)
    H2O
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
BeCl2 has no lone pairs on the beryllium. Thus, the electrons on the chlorides willtry to stay far apart from each other, since their corresponding electrons repel each other (while experiencing no deflection from electrons on a central atom). Thus themolecule is linear in shape.

Hydrogen bonds are formed in many compounds e.g., H2O, HF, NH3 . The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :
  • a)
    HF > H2O > NH3
  • b)
    H2O > HF > NH3
  • c)
    NH3 > HF > H2O ​
  • d)
    NH3 > H2O > HF
Correct answer is option 'B'. Can you explain this answer?

Neha Joshi answered
H2​O>HF>NH3​
Strength of hydrogen bonding depends on the size and electronegativity of the atom. 
Smaller the size of the atom, greater is the electronegativity and hence stronger is the H−bonding. Thus, the order of strength of H-bonding is H...F>H...O>H...N. 
But each HF molecule is linked only to two other HF molecules while each H2O molecule is linked to four other H2​O molecules through H−bonding.
Hence, the decreasing order of boiling points is H2​O>HF>NH3​.

Select the correct statement(s) about benzene (C6H6),
  • a)
    (C=C) bond is shorter than (C—C) bond
  • b)
    All (C— H) bonds are equivalent
  • c)
    C-atom is sp2-hybridised
  • d)
    All (C=C) and (C—C) bonds are of equal stability
Correct answer is option 'B,C,D'. Can you explain this answer?

Suresh Reddy answered
Due to complete-delocalisation of π-electrons, benzene exists as resonance structures.

Thus, (C=C) bonds and (C —C) bonds are of equal length and stability.
All (C— H) bonds are equivalent.
C-atom is also sp2-hybridised.

Among the following the maximum covalent character is shown by the compound 
  • a)
    MgCl2
  • b)
    FeCl2
  • c)
    SnCl2
  • d)
    AlCl3
Correct answer is option 'D'. Can you explain this answer?

Sinjini Pillai answered
Covalent character is a measure of the degree of sharing of electrons between the bonded atoms in a compound. Compounds with high covalent character have a greater degree of electron sharing between the bonded atoms.

Explanation:

MgCl2:
- Mg is a metal and Cl is a non-metal
- The electronegativity difference between Mg and Cl is large, meaning MgCl2 is an ionic compound
- Ionic compounds have low covalent character due to the complete transfer of electrons from the metal to the non-metal

FeCl2:
- Fe is a metal and Cl is a non-metal
- The electronegativity difference between Fe and Cl is moderate, meaning FeCl2 has some ionic character but also some covalent character
- However, the metal in FeCl2 is a transition metal, which can have variable oxidation states and can form complex ions. This makes it difficult to determine the exact degree of covalent character in FeCl2

SnCl2:
- Sn is a metal and Cl is a non-metal
- The electronegativity difference between Sn and Cl is small, meaning SnCl2 has a greater degree of covalent character than MgCl2 or FeCl2
- However, the metal in SnCl2 is not highly electronegative, which means it is less likely to share electrons with the non-metal Cl

AlCl3:
- Al is a metal and Cl is a non-metal
- The electronegativity difference between Al and Cl is moderate, meaning AlCl3 has some ionic character but also some covalent character
- However, AlCl3 is a Lewis acid, which means it can accept a lone pair of electrons from a Lewis base
- This Lewis acid-base interaction results in a greater degree of electron sharing between the Al and Cl atoms in AlCl3, giving it the highest covalent character among the given compounds

Therefore, the correct answer is (d) AlCl3.

Valence bond theory was introduced by:
  • a)
    Gillespie
  • b)
    Heitler 
  • c)
    Pauling
  • d)
    Lewis
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
He then called up his associate Fritz London and they worked out the details of the theory over the course of the night. Later, Linus Pauling used the pair bonding ideas of Lewis together with Heitler–London theory to develop two other key concepts in VB theory: resonance (1928) and orbital hybridization (1930).

In which one of the following species the central atom has the type of hybridisation which si not the same as that present in the other three? 
  • a)
    SF4​
  • b)
    I3-
  • c)
    SbCl52-
  • d)
    PCl5
Correct answer is option 'C'. Can you explain this answer?

Geetika Shah answered
Molecules having the same number of hybrid orbitals, have same hybridisation and number of hybrid oebitals.

where,
V= number of valance electrons of central atom
X = number of monovalent atoms
C= charge on cation
A = charge on anion
 

Which of the following angle corresponds to sp2 hybridisation?
  • a)
    90°
  • b)
    120°
  • c)
    180°
  • d)
    109°
Correct answer is option 'B'. Can you explain this answer?

Arun Yadav answered
sp2 hybridisation gives three sp2 hybrid orbitals which are planar triangular forming an angle of 120DEG with each other.
The electronic configurations of three elements A, B and C are given below.
Answer the questions from 14 to 17 on the basis of these configurations.
A ls2^2s2^2p^6
B ls2^2s2^2p63s23p^3
C ls2^2s2^2p63s^23ps 

Which molecule has a bent shape?
  • a)
    CO2
  • b)
    BeH2
  • c)
    H2O
  • d)
    NF3
Correct answer is option 'C'. Can you explain this answer?

Shreya Singh answered
Oxygen is sp3 hybridised in H2O molecule..... and it should have tetrahedral structure with bond angle  109•28'...but The oxygen has 6 valence electrons and thus needs 2 more electrons from 2 hydrogen atoms to complete its octet. This then leaves two lone electron pairs that are not bonded to any other atoms. ....The 2 lone electron pairs exerts a little extra repulsion on the two bonding hydrogen atoms to create a slight compression to a 104obond angle......and because of this it acquires bent/v/angular shape..

Which of the following structures is more acceptable for HNO3?
  • a)
  • b)
  • c)
    Both equally
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Naina Sharma answered
Structure is decided based on formal charge.

where, v = valence electrons
s = shared electrons
u = unshared electrons


Structure with at least one neutral atom is favoured.

How many bonding MO are used in the formation of NO?
    Correct answer is '5'. Can you explain this answer?

    Vivek Kumar answered
    This question is wrong here its asking for bonding electron but answer is given for anti bonding .......

    Among the following species linear shape is found in:
    • a)
      SO2
    • b)
      O3
    • c)
      NO2+
    • d)
      NO2
    Correct answer is option 'C'. Can you explain this answer?

    Rohit Shah answered
    In NO2(+) i.e. nitronium ion N-atom has sp-hybridisation ; so, it adopts linear geometry & O-N-O bond angle is 180 deg.
    While, in NO2(–) i.e. nitrite ion, N–atom has sp2 hybridisation; so, it adopts bent geometry, for NO2–, actual O-N-O bond angle is 115 deg (yes, it's slightly deviated from expected 120deg because of repulsion between the interacting bond pairs and lone pair of electrons.

    Two atoms are said to be bonded when:
    • a)
      System acquires minimum energy
    • b)
      Potential energy becomes maximum
    • c)
      Magnitude of attractive forces is greater than repulsive forces
    • d)
      Energy becomes zero
    Correct answer is option 'A'. Can you explain this answer?

    Anjana Sharma answered
    Attractive forces tend to bring two atoms close to each other whereas repulsive forces tend to move them away. In hydrogen, the magnitude of the new attractive forces is greater than that of new repulsive forces. As a result, two atoms come close to each other and potential energy decreases. The atoms approach each other until the equilibrium stage is reached where the net force of attraction balances the force of repulsion and system acquires minimum energy. 

     Among the following molecules, the molecule with trigonal planar geometry is:
    • a)
      BF3
    • b)
      IF3
    • c)
      NH3
    • d)
      PCl3
    Correct answer is option 'A'. Can you explain this answer?

    Gaurav Kumar answered
    (a) BF₃ ⇒ 3bp + 0/p ⇒ sp³ -hybridisation and triagonal planar geometry.
    (b) IF₃ ⇒ 3bp + 2/p ⇒ sp³d -hybridisation and T shape.
    (c) NH₃ ⇒ 3bp + 1/p ⇒ sp³ -hybridisation and pyraminal geometry.
    (d) PH₃ ⇒ 3bp + 1/p ⇒ sp³ -hybridisation and pyraminal geometry.

    If one of the electrons in the He2 molecule is taken to the next excited state, then bond order in He2
    • a)
      increases by 1 unit
    • b)
      decreases by 1 unit
    • c)
      increases by 0.5 unit
    • d)
      no change
    Correct answer is option 'A'. Can you explain this answer?

    Gaurav Kumar answered


    Electron is taken to next excited state that is  hen electronic configuration is 

    Number of electrons in bonding molecular orbital = 3
    and in anti-bonding molecular orbital = 1
    Thus, bond order = (3 - 1) /2 =1
    Thus, bond order increases by 1 unit. 

    The statement that is true about H2O molecule is:
    • a)
      It has T-shaped geometry and two lone pair of electrons.
    • b)
      It has V-shaped geometry and two lone pair of electrons.
    • c)
      It has tetrahedral geometry and no lone pair of electrons.
    • d)
      It has pyramidal geometry and one lone pair of electrons.
    Correct answer is option 'B'. Can you explain this answer?

    Geetika Shah answered
    Central atom: O
    At. no. = 8,
    No. of valence electrons in oxygen is 6
    Lewis dot structure of O atom
    No. of electrons required for completing the octet = 8 - 6 =2
    Atoms attached to the central atom: two H atoms
    At. no. of H = 1
    H atoms need one electron each for getting fully-filled K shells.
    Representation of Lewis dot structures of H2O, which satisfies these conditions:
     
    No. of valence shell electron pairs on the central atom O, after forming two covalent bonds with two H atoms = 4.
    Geometry of 4 pairs, as predicted by VSEPR theory = Tetrahedral.
    No. of lone pairs = Two.
    Type, according to VSEPR theory:
    So, geometry of pairs and geometry of atoms are different.
    The geometry of atoms is derived from the geometry of pairs. At two of the four corners of the tetrahedron, there are no atoms.
    Diagrams showing the geometry of 2 H atoms and two lone pairs:
     
    Geometry of atoms in H2O is V-shaped. i.e. H2O molecule has a bent geometry

    Hydrogen bonds are formed in many compounds e.g., H2O, HF, NH3. The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :
    • a)
      HF > H2O > NH3
    • b)
      H2O > HF > NH3
    • c)
      NH3 > HF > H2O
    • d)
      NH3 > H2O > HF
    Correct answer is option 'B'. Can you explain this answer?

    Shreya Gupta answered
    Strength of H-bonding depends on the electronegativity of the atom which follows the order: F > O > N .
    Strength of H-bond is in the order:
    H……. F > H…….. O > H…….. N
    But each H2O molecule is linked to 4 other H2O molecules through H-bonds whereas each HF molecule is linked only to two other HF molecules.
    Hence, correct decreasing order of the boiling points is HzO > HF > NH3.  

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