intro
MCQs 1
Which species among the following has the same configuration as Neon?
Topic: Electron Configuration Similarity in Atomic Species
Correct Answer: A) Na+
- Electron configuration refers to the distribution of electrons in an atom or molecule, which can be similar among different species.
- Here, we are focusing on the neon configuration, represented as 10Ne = 1s2, 2s2, 2p6.
- Comparing the options, we find that Sodium ion (Na+) has the electron configuration 11Na = 1s2, 2s2, 2p6, 3s1, but when it loses an electron to become Na+, its configuration matches that of Neon, i.e., 10Na+ = 1s2, 2s2, 2p6.
- Therefore, the correct answer is A, "Na+", which shares the same electron configuration as Neon after losing one electron.
MCQs 2
Which of the following species has the largest ionic size?
Topic: Ionic Size in Different Atomic Species
Correct Answer: C) N3-
- Ionic size compares the relative sizes of ions in atomic species.
- The rule of thumb is that anions (negative ions) are larger than the neutral form, which in turn is larger than the cation (positive ions).
- Given the options, N3- (negative third ion of Nitrogen) holds the largest size, followed by O2-, F-, and finally Na+.
- Thus, the correct answer is C, "N3-".
MCQs 3
Which among the following species has a completely filled outermost shell in its atomic form?
Topic: Electron Configuration in Different Atomic Species
Correct Answer: A) Noble gases
- The completion of the outermost shell of an atom determines its stability.
- Only the noble gases in the periodic table have a complete outermost shell, making them very stable.
- This is not true for alkali metals, coinage metals, or gun metals.
- Therefore, the correct answer is A, "Noble gases".
Question 4:
What is the geometry of the PF5 molecule?
Topic: Molecular Geometry in Chemical Species
Correct Answer: C) Trigonal bipyramidal
- Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule.
- For the PF5 (Phosphorus Pentafluoride) molecule, the geometry is trigonal bipyramidal.
- This type of geometry involves one atom at the center with five surrounding atoms at the corners of a triangular bipyramid.
- Therefore, the correct answer is C, "Trigonal bipyramidal".
Question 5:
Which of the following statements is NOT true regarding the difference between sigma bonds and pi bonds?
Topic: Differences between Sigma Bonds and Pi Bonds
Correct Answer: B) Pi bonds allow free rotation about the inter-nuclear axis
- Sigma and pi bonds are types of covalent bonds that differ in their properties.
- Sigma bonds allow free rotation around the bond axis, enabling the bonded atoms to rotate freely relative to each other.
- In contrast, Pi bonds restrict this rotation due to the parallel orbital alignment.
- Therefore, the statement B, "Pi bonds allow free rotation about the inter-nuclear axis", is incorrect.
Question 6:
How many types and quantities of bonds are present in nitrogen molecules?
Topic: Bond Types in Nitrogen Molecules
Correct Answer: B) One σ and two π
- Nitrogen molecules contain a triple bond, which consists of various bond types.
- This triple bond includes one sigma (σ) bond and two pi (π) bonds.
- Sigma bonds are formed by the end-to-end overlapping of atomic orbitals, while pi bonds are formed by the side-by-side overlapping.
- Thus, option B, "One σ and two π", correctly describes the bonding in nitrogen molecules.
Question 7:
Which group of elements is considered the most stable among all elements?
Topic: Element Stability Across the Periodic Table
Correct Answer: D) Noble gases
- The stability of elements is determined by the electron configuration in their outermost shell.
- Noble gases are unique because they have a full valence electron shell, leading to extreme stability and a minimal tendency to form chemical bonds.
- This characteristic distinguishes them from other groups such as halogens, alkali metals, and alkaline earth metals.
- Therefore, the correct answer is D, "Noble gases".
MCQ 8:
What is the geometry of an ammonia (NH3) molecule?
Topic: Molecular Geometry of Ammonia
Correct Answer: D) Trigonal Pyramidal
- Ammonia (NH3) consists of one nitrogen atom and three hydrogen atoms.
- The nitrogen atom in ammonia has three bond pairs and one lone pair of electrons, resulting in a trigonal pyramidal molecular geometry.
- Therefore, the correct answer is D, "Trigonal Pyramidal".
MCQ 9:
What is the geometry of an ethene (C2H4) molecule?
Topic: Molecular Geometry of Ethene
Correct Answer: B) Trigonal planar
- Ethene (C2H4) consists of two carbon atoms and four hydrogen atoms.
- Each carbon atom in ethene is sp2 hybridized, resulting in a trigonal planar molecular geometry with a bond angle of 120°.
- Therefore, the correct answer is B, "Trigonal Planar".
MCQ 10:
Which of the following best describes the molecular geometry of water (H2O)?
Topic: Molecular Geometry of Water
Correct Answer: D) Bent or Angular
- Water (H2O) consists of two hydrogen atoms and one oxygen atom.
- The oxygen atom in water has two bond pairs and two lone pairs of electrons, resulting in a bent or angular molecular geometry.
- Therefore, the correct answer is D, "Bent or Angular".
MCQ 11:
What shared attributes characterize hybrid orbitals?
Topic: Properties of Hybrid Orbitals
Correct Answer: C) Both shape and energy are identical across hybrid orbitals
- Hybrid orbitals are characterized by identical energy levels and shapes.
- Regardless of the type of hybridization (sp, sp2, sp3, etc.), all resulting hybrid orbitals in a given atom will be equivalent in shape and energy.
- Consequently, option C, "Both shape and energy are identical across hybrid orbitals," correctly describes the properties of hybrid orbitals.
MCQ 12:
Which characteristic does not apply to ionic compounds?
Topic: Properties of Ionic Compounds
Correct Answer: D) They exhibit isomerism
- Ionic compounds are solid-state non-conductors, can conduct electricity when molten, and exhibit polymorphism.
- However, they do not exhibit isomerism, which is a characteristic primarily associated with covalent compounds.
- Hence, the correct answer is D, "They exhibit isomerism".
MCQ 13:
How does electronegativity vary across a period from left to right?
Topic: Periodic Trends in Electronegativity
Correct Answer: A) It increases
- Electronegativity increases across a period from left to right due to an increase in nuclear charge and a decrease in atomic radius.
- Therefore, the correct answer is A, "It increases".
MCQ 14:
Which of the following is not a characteristic of ionic compounds?
Topic: Characteristic Features of Ionic Compounds
Correct Answer: A) They exist exclusively in the solid state
- Ionic compounds are primarily found in the solid state but can conduct electricity when molten.
- They exhibit polymorphism and isomerism.
- However, their bonds are non-directional and non-rigid.
- The characteristic that does not apply to ionic compounds is that they exist exclusively in the solid state.
Question 15:
Which statement correctly describes the reactivity of ionic and covalent compounds?
Topic: Reactivity of Covalent and Ionic Compounds
Correct Answer: B) The reactivity of covalent compounds is less than ionic compounds
- The reactivity of a compound depends on the type of bonding it exhibits.
- Ionic reactions generally occur faster than covalent reactions because ionic reactions merely require the rearrangement of ions, which is energetically favorable.
- In contrast, covalent reactions involve breaking and forming new bonds, which is a slower process.
- Therefore, the reactivity of covalent compounds is less than that of ionic compounds.
Question 16:
Why is a σ-bond stronger than a π bond?
Topic: σ and π Bond Strengths
Correct Answer: C) σ-bond has electron density between the nuclei
- The strength of a chemical bond is determined by the location of the electron density.
- In a σ-bond, the electron density is located between the nuclei which results in a strong electrostatic attraction between the electrons and the nuclei.
- On the other hand, π-bonds have their electron density above and below the plane of the nuclei, leading to a weaker interaction between the electrons and the nuclei.
- Therefore, σ-bonds are stronger than π-bonds.
Question 17:
Which of the following is not a periodic property?
Topic: Periodic Properties of Elements
Correct Answer: C) Dipole moment
- Periodic properties are those which display a pattern or trend as we move across the periods or down the groups in the periodic table.
- Ionization energy, atomic radius, and electron affinity are all examples of periodic properties as their values change in a predictable manner along periods.
- Dipole moment, on the other hand, is not a periodic property as it does not show a predictable trend in the periodic table, but rather depends on the molecular structure and the difference in electronegativity between bonded atoms.
Question 18:
What is the geometry of BeCl2?
Topic: Molecular Geometry
Correct Answer: A) Linear
- The geometry of a molecule is determined by the number of electron pairs around the central atom.
- In BeCl2, Beryllium (Be) is the central atom, bonded with two Chlorine (Cl) atoms.
- Beryllium forms two bonds and does not have any lone pairs of electrons, which leads to a linear geometry with a bond angle of 180˚.
- Thus, the geometry of BeCl2 is linear.
Question 19:
Which of the following elements is the most stable?
Topic: Elemental Stability
Correct Answer: C) Helium
- The stability of an element is related to its electron configuration, particularly the arrangement of electrons in its valence shell.
- Helium is a noble gas with a completely filled valence shell, making it extremely stable and unreactive.
- Additionally, helium has the highest ionization energy in the periodic table, which further indicates its high stability.
- Therefore, among the given options, Helium is the most stable element.
Question 20:
Which of these diatomic molecules forms the strongest bond, given their bond energies as F2 (37 kcal), Cl2 (58 kcal), Br2 (46 kcal), and I2 (36 kcal)?
Topic: Bond Energies
Correct Answer: B) Cl₂
- The bond strength of a molecule can be inferred from its bond energy – the more energy required to break a bond, the stronger it is.
- Comparing the given bond energies, it is evident that Cl2 has the highest bond energy (58 kcal), indicating the strongest bond.
- The sequence of bond strength in halogens according to the given values is Cl2 > Br2 > F2 > I2.
- Therefore, Cl₂ forms the strongest bond among the given options.
Question 21:
In what scenario is a bond considered ionic, based on the electronegativity difference of the bonded atoms?
Topic: Determining Ionic and Covalent Bonds
Correct Answer: B) Electronegativity difference is greater than 1.7
- The nature of a bond (ionic or covalent) can be determined by the difference in electronegativity between the bonded atoms.
- If the electronegativity difference is greater than 1.7, the bond is generally considered ionic.
- Conversely, if the electronegativity difference is less than 1.7, the bond is typically covalent.
- Hence, for a bond to be ionic, the electronegativity difference should be greater than 1.7.
Question 22:
How many electrons are shared in SF6 molecule?
Topic: Bond Formation and Electron Sharing
Correct Answer: B) 12
- The number of shared electrons in a molecule depends on the number of covalent bonds formed.
- In SF6, sulfur (S), the central atom, forms six covalent bonds with six fluorine (F) atoms.
- Since each covalent bond involves sharing of two electrons, there are 2*6 = 12 shared electrons.
- Thus, in an SF6 molecule, a total of 12 electrons are shared.
Question 23:
Identify the molecule among the following that adopts a planar geometry:
Topic: Molecular Geometries
Correct Answer: A) Formaldehyde
- The geometry of a molecule is determined by the arrangement of its atoms in space.
- Of the listed options, formaldehyde is the molecule that exhibits a planar geometry.
- This is due to its trigonal planar arrangement of atoms where the carbon atom is at the center, bonded to two hydrogen atoms and one oxygen atom.
- Therefore, Formaldehyde is the planar molecule among the given options.
Question 24:
Why is the H – O – H bond angle in H2O 104.5˚ rather than the typical tetrahedral angle of 109.28˚?
Topic: Bond Angles and Repulsion
Correct Answer: D) Lone pair – Bond pair repulsion
- The bond angle in a molecule is influenced by both the electronegativity of the atoms and the repulsion between electron pairs.
- In water (H2O), the bond angle is less than the typical tetrahedral angle (109.28˚) because of lone pair – bond pair repulsion.
- The repulsion between the lone pairs and the bond pairs of electrons pushes the bond pairs closer together, reducing the bond angle to 104.5˚.
- Thus, the H-O-H bond angle in water is 104.5˚ due to lone pair – bond pair repulsion.
Question 25:
Which pair amongst the following exhibits the same trend in the periodic table?
Topic: Periodic Trends
Correct Answer: B) Electronegativity and Ionization energy
- Certain properties of elements exhibit consistent patterns or trends on the periodic table.
- Of the given pairs, "Electronegativity and Ionization energy" exhibit the same trend: they both increase across a period and decrease down a group.
- This is because both properties depend on the nuclear charge and the distance of the valence electrons from the nucleus.
- Therefore, Electronegativity and Ionization energy have the same trend in the periodic table.
Question 26:
Which of the following elements has the highest electronegativity value according to the Pauling scale?
Topic: Electronegativity
Correct Answer: D) Fluorine
- Electronegativity refers to the ability of an atom to attract shared electrons in a covalent bond.
- On the Pauling scale, Fluorine is given the highest electronegativity value of 4.
- This implies that Fluorine has the greatest ability to attract electrons towards itself among all elements.
- Therefore, the element with the highest electronegativity value is Fluorine.
Question 27:
Which of the following statements does not accurately describe covalent compounds?
Topic: Properties of Covalent Compounds
Correct Answer: B) Non-directional nature
- Covalent compounds have certain characteristic properties.
- One such property is the directional nature of their bonds, unlike ionic compounds which are non-directional.
- Another property is their solubility in non-polar solvents like benzene, and that they generally exhibit slower reactions compared to ionic compounds.
- Therefore, the non-directional nature does not belong to the properties of covalent compounds.
Question 28:
Which type of bond results when a shared pair of electrons is donated by just one of the bonded atoms?
Topic: Types of Bonds
Correct Answer: C) Coordinate Covalent Bond
- There exist different types of chemical bonds based on how electrons are shared or transferred between atoms.
- A Coordinate Covalent Bond is unique because it involves one atom donating a pair of electrons towards the bond formation.
- The atom that provides both electrons in the bond is called the donor, while the other atom is the acceptor.
- Hence, the bond formed when one of the bonded atoms donates a shared pair of electrons is a Coordinate Covalent Bond.
Question 29:
Identify the statement where the characteristics of ionic and covalent bonds are incorrectly paired:
Topic: Ionic and Covalent Bonds
Correct Answer: C) Statement C
- Ionic and covalent bonds represent two extremes in the types of chemical bonds.
- Covalent bonds occur when electrons are shared between atoms, while ionic bonds are formed when electrons are transferred between atoms.
- Understanding the properties of these bonds is crucial to properly classify them.
- Hence, Statement C does not accurately represent the properties of either ionic or covalent bonds.
Question 30:
Which type of elements typically exhibit low ionization energy values?
Topic: Ionization Energy
Correct Answer: A) Metals
- Ionization energy is a measure of the energy required to remove an electron from an atom or ion.
- Metals, being electropositive in nature, generally exhibit lower ionization energies compared to non-metals.
- This is because metals are more willing to lose electrons and form positive ions.
- Therefore, metals typically exhibit lower ionization energy values.