Chemical Bonding and Compounds Competitive Exams
100 questions · General Science
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Question 1 of 100
The formula CuSO₄·5H₂O represents:
ExplanationThe dot notation indicates water molecules associated with the crystal structure; this formula represents copper sulfate with 5 water molecules per formula unit.
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Question 2 of 100
Metals are good conductors of electricity primarily because of:
ExplanationMetallic bonding involves a 'sea' of delocalized electrons that can move freely throughout the metal lattice, enabling electrical conductivity.
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Question 3 of 100
Metal oxides generally react with water to form:
ExplanationMetal oxides are generally basic and react with water to form metal hydroxides (bases).
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Question 4 of 100
Why is diamond extremely hard while graphite is soft and slippery, despite both being pure carbon?
ExplanationDiamond's tetrahedral 3D covalent network makes it extremely hard, while graphite's layered structure (held together by weak forces between layers) allows layers to slide, making it soft and slippery.
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Question 5 of 100
The strength of intermolecular forces in a substance directly affects its:
ExplanationStronger intermolecular forces require more energy to overcome, resulting in higher boiling and melting points for a substance.
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Question 6 of 100
Non-metal oxides generally react with water to form:
ExplanationNon-metal oxides are generally acidic and react with water to form acids (e.g., CO₂ + H₂O → H₂CO₃).
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Question 7 of 100
Network covalent solids (like diamond) are characterized by:
ExplanationNetwork covalent solids like diamond consist of atoms covalently bonded in a continuous 3D lattice, resulting in very high melting points and great hardness.
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Question 8 of 100
A polar covalent bond occurs when atoms share electrons:
ExplanationA polar covalent bond forms when atoms have different electronegativities, causing unequal sharing of electrons and partial charges.
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Question 9 of 100
A double covalent bond consists of:
ExplanationA double bond is made up of one sigma bond and one pi bond, as seen in C=C or O=O.
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Question 10 of 100
The oxidation state of oxygen in most compounds is:
ExplanationOxygen typically has an oxidation state of −2 in most compounds, except in peroxides (−1) and when bonded to fluorine.
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Question 11 of 100
Which of the following best explains the very high melting point of silicon dioxide (SiO₂) compared to carbon dioxide (CO₂)?
ExplanationSiO₂'s giant covalent structure requires breaking numerous strong Si-O covalent bonds to melt, while CO₂ exists as separate molecules held together only by weak Van der Waals forces, requiring much less energy to overcome.
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Question 12 of 100
Ionic compounds generally have __________ melting and boiling points compared to covalent molecular compounds.
ExplanationIonic compounds have strong electrostatic forces between ions, requiring more energy (higher temperatures) to overcome, giving higher melting/boiling points than most covalent molecular compounds.
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Question 13 of 100
Covalent bonds typically form between:
ExplanationCovalent bonding typically occurs between two nonmetal atoms sharing electrons.
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Question 14 of 100
The general trend that 'like dissolves like' in chemistry refers to the principle that:
ExplanationThis principle explains solubility patterns: substances with similar polarity (polar-polar or nonpolar-nonpolar) tend to be more soluble in each other.
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Question 15 of 100
Which of the following is an example of an inorganic compound?
ExplanationInorganic compounds generally do not contain carbon-hydrogen bonds; sodium chloride is a classic inorganic ionic compound.
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Question 16 of 100
The oxidation state of hydrogen in most compounds is:
ExplanationHydrogen typically has an oxidation state of +1 in most compounds, except in metal hydrides where it is −1.
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Question 17 of 100
An amphoteric oxide, such as aluminum oxide, can react with:
ExplanationAmphoteric oxides exhibit dual character, reacting with both acids and bases to form salts and water.
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Question 18 of 100
Which of the following substances exhibits hydrogen bonding?
ExplanationWater molecules exhibit hydrogen bonding due to O-H bonds and lone pairs on oxygen; methane, CO2, and N2 lack this capability.
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Question 19 of 100
Allotropes of an element are different structural forms of the:
ExplanationAllotropes are different structural forms of the same element, such as diamond and graphite, both being allotropes of carbon.
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Question 20 of 100
A chemical bond is formed due to:
ExplanationAtoms form chemical bonds to attain a more stable, lower-energy electron configuration, often resembling noble gases (octet rule).
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Question 21 of 100
The 'octet rule' states that atoms tend to gain, lose, or share electrons to have:
ExplanationThe octet rule states atoms are most stable with eight valence electrons, resembling the electron configuration of noble gases (except H and He, which follow a duet rule).
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Question 22 of 100
What is the oxidation state of manganese (Mn) in KMnO₄?
ExplanationIn KMnO₄: K is +1, O is −2 (×4 = −8). For neutrality: +1 + Mn + (−8) = 0, so Mn = +7.
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Question 23 of 100
Which of the following is formed as a byproduct when an acid reacts with a base (neutralization)?
ExplanationA typical acid-base neutralization reaction produces a salt and water as products.
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Question 24 of 100
Bond length is generally defined as the:
ExplanationBond length is the average equilibrium distance between the centers (nuclei) of two atoms joined by a chemical bond.
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Question 25 of 100
Which of the following is a binary compound?
ExplanationA binary compound contains only two different elements; NaCl consists of sodium and chlorine only.
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Question 26 of 100
Bond energy is defined as the energy required to:
ExplanationBond energy (or bond dissociation energy) is the energy needed to break one mole of a specific covalent bond between two atoms in the gas phase.
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Question 27 of 100
A pi (π) bond is formed by the:
ExplanationA pi bond forms from the sideways overlap of parallel unhybridized p orbitals, typically found in double and triple bonds, restricting free rotation.
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Question 28 of 100
Hybridization involving one s and three p orbitals is called:
Explanationsp³ hybridization combines one s and three p orbitals, forming four hybrid orbitals arranged tetrahedrally (e.g., in methane, CH₄).
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Question 29 of 100
According to the Bronsted-Lowry theory, a base is defined as a:
ExplanationBronsted-Lowry theory defines a base as any substance capable of accepting a proton (H⁺) from an acid.
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Question 30 of 100
Hybridization involving one s and one p orbital is called:
Explanationsp hybridization combines one s and one p orbital, forming two hybrid orbitals arranged linearly (e.g., in acetylene, C₂H₂).
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Question 31 of 100
London dispersion forces arise due to:
ExplanationLondon dispersion forces are temporary attractive forces caused by momentary fluctuations in electron distribution, creating instantaneous dipoles.
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Question 32 of 100
The oxidation state of an element in its free, uncombined state is:
ExplanationElements in their free, uncombined elemental form (like O₂, Fe, Na) have an oxidation state of zero.
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Question 33 of 100
Covalent molecular compounds generally have __________ melting and boiling points compared to ionic compounds.
ExplanationCovalent molecular compounds are held together by weaker intermolecular forces, resulting in generally lower melting and boiling points than ionic compounds.
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Question 34 of 100
Ionic compounds conduct electricity when:
ExplanationIonic compounds conduct electricity only when ions are free to move, such as when dissolved in water or melted, but not in rigid solid form.
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Question 35 of 100
A covalent bond is formed by the:
ExplanationCovalent bonds form when two atoms share one or more pairs of electrons, typically between nonmetal atoms.
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Question 36 of 100
An ionic bond is formed by the:
ExplanationIonic bonds form when electrons are completely transferred from a metal atom to a nonmetal atom, creating oppositely charged ions that attract each other.
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Question 37 of 100
A sigma (σ) bond is formed by the:
ExplanationA sigma bond forms from the direct, head-on overlap of orbitals along the bond axis, allowing free rotation.
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Question 38 of 100
Which of the following best describes an ionic compound's typical physical state at room temperature?
ExplanationIonic compounds typically form hard, crystalline solids at room temperature due to strong electrostatic forces between ions in a lattice.
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Question 39 of 100
A salt is formed when an acid reacts with a:
ExplanationA neutralization reaction between an acid and a base produces a salt and water.
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Question 40 of 100
Graphite, an allotrope of carbon, conducts electricity due to:
ExplanationIn graphite, each carbon atom is covalently bonded to three others in layers, leaving one delocalized electron per atom that can move freely, allowing electrical conductivity.
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Question 41 of 100
A crystal lattice refers to the:
ExplanationA crystal lattice is the highly ordered, repeating three-dimensional geometric arrangement of atoms, ions, or molecules in a crystalline solid.
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Question 42 of 100
A molecule with four bonding pairs and no lone pairs on the central atom (like CH₄) typically has what shape?
ExplanationFour bonding pairs with no lone pairs arrange in a tetrahedral geometry with bond angles of approximately 109.5°.
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Question 43 of 100
A molecule with three bonding pairs and one lone pair on the central atom (like NH₃) typically has what shape?
ExplanationAmmonia has three bonding pairs and one lone pair; the lone pair distorts the tetrahedral arrangement into a trigonal pyramidal shape.
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Question 44 of 100
The chemical formula of hydrochloric acid is:
ExplanationHydrochloric acid consists of one hydrogen atom and one chlorine atom, giving the formula HCl.
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Question 45 of 100
A compound is a substance formed when two or more elements combine in a:
ExplanationCompounds consist of two or more elements chemically combined in a fixed, definite ratio.
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Question 46 of 100
Which type of compound generally has a 'network' structure extending infinitely in three dimensions, such as quartz (SiO₂)?
ExplanationQuartz (SiO₂) is a network covalent solid where silicon and oxygen atoms are covalently bonded in a continuous 3D lattice, unlike simple discrete molecules.
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Question 47 of 100
Which of the following best describes a 'molecular formula'?
ExplanationThe molecular formula gives the exact number of atoms of each element present in a single molecule (e.g., C₆H₁₂O₆ for glucose).
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Question 48 of 100
Which of the following is an example of a coordinate covalent bond?
ExplanationIn NH₄⁺, the nitrogen atom's lone pair is donated to a hydrogen ion (H⁺), forming a coordinate covalent bond.
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Question 49 of 100
VSEPR theory is used to predict the:
ExplanationValence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular geometry based on minimizing repulsion between electron pairs around a central atom.
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Question 50 of 100
Which of the following is an example of an organic compound?
ExplanationOrganic compounds generally contain carbon bonded to hydrogen (and often other elements); methane is a simple hydrocarbon, an organic compound.
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Question 51 of 100
Diamond and graphite are both allotropes of which element?
ExplanationDiamond and graphite are both composed entirely of carbon atoms but differ in their structural arrangement and bonding.
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Question 52 of 100
As bond order increases (e.g., single to double to triple bond), bond length generally:
ExplanationHigher bond order means more shared electron pairs, pulling atoms closer together and decreasing bond length.
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Question 53 of 100
The chemical formula of sodium bicarbonate (baking soda) is:
ExplanationSodium bicarbonate's formula is NaHCO₃, containing sodium, hydrogen, carbon, and oxygen.
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Question 54 of 100
Van der Waals forces are generally __________ compared to ionic or covalent bonds.
ExplanationVan der Waals forces are weak intermolecular forces, significantly weaker than ionic or covalent bonds within a molecule.
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Question 55 of 100
Which of the following molecules is nonpolar despite containing polar bonds?
ExplanationCO₂ has polar C=O bonds, but its linear symmetric shape causes the bond dipoles to cancel, making the overall molecule nonpolar.
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Question 56 of 100
A bond is generally considered ionic if the electronegativity difference between atoms is approximately:
ExplanationA common rule of thumb: electronegativity difference > 1.7 suggests predominantly ionic character; 0.4–1.7 suggests polar covalent; < 0.4 suggests nonpolar covalent.
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Question 57 of 100
A molecule can have polar bonds but still be nonpolar overall if:
ExplanationSymmetrical molecules (like CO₂) can have polar bonds that cancel out due to their geometric arrangement, resulting in a net dipole moment of zero (nonpolar molecule).
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Question 58 of 100
A molecule with two bonding pairs and no lone pairs on the central atom (like BeCl₂) typically has what shape?
ExplanationWith two bonding pairs and no lone pairs, repulsion is minimized in a straight line, giving a linear (180°) molecular geometry.
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Question 59 of 100
Which of the following best explains why ionic compounds are often soluble in water (polar solvent)?
ExplanationPolar water molecules surround and stabilize individual ions (a process called hydration), pulling them away from the crystal lattice and into solution.
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Question 60 of 100
A Lewis structure (electron dot diagram) represents:
ExplanationLewis structures show valence electrons as dots around atomic symbols, illustrating bonding and lone pairs in a molecule.
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Question 61 of 100
A triple covalent bond consists of:
ExplanationA triple bond, such as in N≡N or C≡C, consists of one sigma bond and two pi bonds.
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Question 62 of 100
Coordination compounds typically consist of a central metal atom/ion surrounded by:
ExplanationCoordination compounds feature a central metal ion bonded to surrounding ligands through coordinate covalent bonds.
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Question 63 of 100
What is the correct formula for magnesium chloride, given Mg²⁺ and Cl⁻ ions?
ExplanationTo balance charges (2+ and 1−), we need 2 chloride ions for each magnesium ion, giving MgCl₂.
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Question 64 of 100
Which of the following best describes the electrical conductivity of covalent molecular compounds?
ExplanationCovalent molecular compounds typically do not conduct electricity since they lack free ions or delocalized electrons.
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Question 65 of 100
To write a correct chemical formula from valency, the total positive charge must:
ExplanationA compound's formula must be electrically neutral, so the total positive charge (from cations) must balance the total negative charge (from anions).
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Question 66 of 100
Hybridization involving one s and two p orbitals is called:
Explanationsp² hybridization combines one s and two p orbitals, forming three hybrid orbitals arranged trigonally (e.g., in ethylene, BF₃).
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Question 67 of 100
The chemical formula of calcium carbonate is:
ExplanationCalcium carbonate consists of one calcium ion, one carbon atom, and three oxygen atoms, giving the formula CaCO₃.
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Question 68 of 100
The bonding in metal carbonyls (like Ni(CO)₄) primarily involves:
ExplanationIn metal carbonyls, carbon monoxide acts as a ligand, donating an electron pair to the metal atom through a coordinate covalent bond.
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Question 69 of 100
Resonance structures are used to represent molecules where:
ExplanationResonance describes molecules (like ozone, O₃) whose true electronic structure is a weighted average (hybrid) of multiple valid Lewis structures, not oscillation between them.
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Question 70 of 100
Ionic bonds typically form between:
ExplanationIonic bonding occurs between metals (which lose electrons easily) and nonmetals (which gain electrons easily).
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Question 71 of 100
According to the Lewis theory, an acid is defined as a substance that:
ExplanationLewis theory, the broadest definition, defines an acid as any species that can accept a pair of electrons, and a base as one that donates a pair of electrons.
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Question 72 of 100
Metallic bonding is best described as:
ExplanationMetallic bonding involves delocalized valence electrons forming a 'sea of electrons' that move freely around a lattice of positive metal ions.
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Question 73 of 100
The pH scale ranges from:
ExplanationThe pH scale conventionally ranges from 0 (strongly acidic) to 14 (strongly basic), with 7 being neutral.
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Question 74 of 100
Pure water at room temperature has a pH of approximately:
ExplanationPure water is neutral, with equal concentrations of H⁺ and OH⁻ ions, giving a pH of 7.
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Question 75 of 100
What is the correct formula for aluminum oxide, given Al³⁺ and O²⁻ ions?
ExplanationTo balance charges (3+ and 2−), we need 2 aluminum ions (total +6) and 3 oxide ions (total −6), giving Al₂O₃.
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Question 76 of 100
An 'anhydrous' compound is one that:
ExplanationAnhydrous compounds lack water of crystallization or any associated water molecules.
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Question 77 of 100
Hydrogen bonding occurs between a hydrogen atom bonded to a highly electronegative atom and:
ExplanationHydrogen bonds form between a hydrogen atom covalently bonded to N, O, or F and a lone pair on another electronegative N, O, or F atom.
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Question 78 of 100
According to the Arrhenius definition, a base is a substance that:
ExplanationArrhenius defined bases as substances that increase the concentration of OH⁻ ions when dissolved in water.
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Question 79 of 100
Which of the following best distinguishes a 'mixture' from a 'compound'?
ExplanationCompounds are chemically bonded with fixed composition and distinct new properties, while mixtures are physically combined, retain individual properties, and can have variable composition.
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Question 80 of 100
Rust (iron oxide) is formed through which type of process?
ExplanationRusting is a chemical reaction where iron reacts with oxygen (and moisture) to form iron oxide (rust), a new compound.
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Question 81 of 100
A solution with a pH less than 7 is:
ExplanationpH values below 7 indicate an acidic solution, with higher H⁺ ion concentration.
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Question 82 of 100
Metals are malleable and ductile mainly because:
ExplanationThe non-directional nature of metallic bonding allows layers of metal cations to slide past each other while the delocalized electron sea maintains the bond, giving malleability and ductility.
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Question 83 of 100
Dipole moment is a measure of:
ExplanationDipole moment quantifies the separation of positive and negative charge within a bond or molecule, indicating its degree of polarity.
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Question 84 of 100
A solution with a pH greater than 7 is:
ExplanationpH values above 7 indicate a basic (alkaline) solution, with higher OH⁻ ion concentration.
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Question 85 of 100
The chemical formula of ammonia is:
ExplanationAmmonia consists of one nitrogen atom bonded to three hydrogen atoms, giving the formula NH₃.
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Question 86 of 100
Which of the following compounds has the empirical formula CH₂ but a different molecular formula?
ExplanationEthylene's molecular formula C₂H₄ simplifies to the empirical formula CH₂ (ratio 1:2).
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Question 87 of 100
According to VSEPR theory, electron pairs around a central atom arrange themselves to:
ExplanationVSEPR theory is based on electron pairs (bonding and lone pairs) arranging as far apart as possible to minimize electrostatic repulsion.
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Question 88 of 100
The chemical formula of sulfuric acid is:
ExplanationSulfuric acid has the formula H₂SO₄, consisting of two hydrogen atoms, one sulfur atom, and four oxygen atoms.
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Question 89 of 100
A 'hydrate' is a compound that:
ExplanationA hydrate incorporates a fixed number of water molecules within its crystalline structure, such as CuSO₄·5H₂O (copper sulfate pentahydrate).
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Question 90 of 100
Covalent (molecular) compounds are often more soluble in __________ solvents due to similar polarity.
ExplanationFollowing the principle 'like dissolves like,' many nonpolar covalent compounds dissolve better in nonpolar solvents rather than polar water.
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Question 91 of 100
A coordinate (dative) covalent bond is formed when:
ExplanationIn a coordinate (dative) bond, one atom donates both electrons of the shared pair, unlike a normal covalent bond where each atom contributes one electron.
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Question 92 of 100
According to the Bronsted-Lowry theory, an acid is defined as a:
ExplanationBronsted-Lowry theory broadens the acid definition to any substance that donates a proton (H⁺) to another substance.
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Question 93 of 100
Which of the following is a common example of a salt?
ExplanationSodium chloride (table salt) is a classic example of a salt, formed from the neutralization of an acid and a base.
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Question 94 of 100
As bond order increases, bond energy (strength) generally:
ExplanationHigher bond order corresponds to stronger bonds, requiring more energy to break, hence increasing bond energy.
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Question 95 of 100
According to the Arrhenius definition, an acid is a substance that:
ExplanationArrhenius defined acids as substances that increase the concentration of H⁺ ions when dissolved in water.
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Question 96 of 100
Dipole-dipole interactions occur between molecules that have:
ExplanationDipole-dipole forces occur between polar molecules that have a permanent separation of positive and negative charge.
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Question 97 of 100
A molecule with two bonding pairs and two lone pairs on the central atom (like H₂O) typically has what shape?
ExplanationWater has two bonding pairs and two lone pairs; the lone pairs cause a bent molecular shape with a bond angle of about 104.5°.
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Question 98 of 100
A nonpolar covalent bond occurs when atoms share electrons:
ExplanationIn a nonpolar covalent bond, atoms of similar or identical electronegativity share electrons equally, with no significant charge separation.
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Question 99 of 100
A single covalent bond consists of:
ExplanationA single bond is composed of just one sigma bond.
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Question 100 of 100
What is the oxidation state of chromium (Cr) in K₂Cr₂O₇?
ExplanationIn K₂Cr₂O₇: K is +1 (×2=+2), O is −2 (×7=−14). For neutrality: +2 + 2(Cr) + (−14) = 0, so 2(Cr) = 12, Cr = +6.
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