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Chemistry HOTS MCQs help revise important concepts and topics.
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CHEMISTRY: CHALLENGING HOTS MCQsSpread the Happiness Feedback: 9008271516 https://t.me/R_Inayathullah_Best_Wishes
Which transition element exhibits the most stable +3 oxidation state and is unlikely to form paramagnetic
complexes?
(a) Mn (b) Fe (c) Co (d) V
An element 'X' readily forms small cations that fit into the voids of a metal lattice. What property of X would
favor the formation of the most stable interstitial compound?
(a) High ionization energy
(b) Low atomic radius
(c) High electronegativity
(d) Metallic character
A coordination complex of a d¹⁰ transition metal ion with octahedral geometry exhibits a yellow color.
Which crystal field splitting diagram best represents this complex?
(a) Large Δ , high spin
(b) Large Δ , low spin
(c) Small Δ , high spin
(d) Small Δ , low spin
Due to the presence of partially filled d-orbitals, all transition elements exhibit catalytic properties.
(a) The statement is always true.
(b) The statement is true for most elements, but exceptions exist.
(c) The statement is only true for elements in higher oxidation states.
(d) The statement is incorrect.
Which transition element exhibits a wider range of stable oxidation states?
(a) Mn (b) Cu (c) Zn (d) Cr
How does the presence of partially filled d-orbitals in transition elements contribute to their catalytic
activity?
(a) They readily form ionic bonds.
(b) They can form multiple oxidation states.
(c) They can accept lone pairs from reactants.
(d) They possess variable radii.
A coordination complex with a d⁶ central metal ion in an octahedral crystal field absorbs red light. What is
the MOST PROBABLE color observed for the complex?
(a) Red (b) Blue (c) Green (d) Yellow
A molecule with the central atom E has four bonded atoms and one lone pair. VSEPR theory predicts a
seesaw molecular geometry. What is the MOST PROBABLE condition for this molecule to be polar?
(a) E is highly electronegative.
(b) All four bonded atoms are identical.
(c) The lone pair is on an axial position.
(d) The molecule exhibits metallic bonding.
Consider two carboxylic acids, A (CH3COOH) and B (ClCH2COOH). Which acid would exhibit higher
acidity, and why?
(a) A, due to a more extensive delocalized electron system.
(b) A, due to the presence of three electronegative atoms around the carboxyl group.
(c) B, due to the presence of chlorine inducing an electron-withdrawing effect.
(d) B, because it has a larger molecular size.
An octahedral complex, [M(en)2X2]^{+}, (where en = ethylenediamine) exhibits optical isomers. What type
of isomerism is MOST LIKELY responsible for this observation?
(a) Geometrical isomerism (b) Linkage isomerism (c) Ionization isomerism (d) Enantiomerism
The formula n(M) = m/M gives the number of moles (n) of a substance with mass (m) and molar mass (M).
Can this formula be directly applied to find the number of atoms in a given sample?
(a) Yes, by using the Avogadro constant in place of M.
(b) Yes, if the mass of individual atoms is known.
(c) No, it only applies to macroscopic quantities.
(d) No, it requires the volume of the substance.
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, CHEMISTRY: CHALLENGING HOTS MCQs
Spread the Happiness Feedback: 9008271516 https://t.me/R_Inayathullah_Best_Wishes
In an octahedral complex of a first-row transition metal ion (M), which ligand would result in the MOST
STABLE complex AND exhibit the strongest absorption of green light?
(a) F (weak field ligand) (b) Cl (weak field ligand) (c) NH3 (strong field ligand) (d) H2O (weak field ligand)
The heat of formation (ΔHf) for CO2(g) is more negative than that of CO(g). However, the C-O bond
strength is higher in CO than in CO2. Explain this observation.
(a) Bond strength and ΔHf always have the same sign.
(b) Breaking stronger bonds in CO releases more energy (positive ΔHf).
(c) Formation of multiple bonds (CO2) from weaker single bonds (CO) releases more energy (negative ΔHf).
(d) The overall ΔHf considers not just bond breaking but also atomic arrangements in the product molecule.
Butan-1-ol can be converted to 1-bromobutane. Which reagent combination would be the MOST
SELECTIVE for this transformation under mild conditions?
(a) HI, heat (b) SOCl2 (c) PBr3 (d) HBr, heat
Friedel-Crafts acylation is a useful method for preparing aromatic ketones. However, under certain
conditions, it can lead to over-acylation. Suggest a way to minimize over-acylation.
(a) Using a large excess of the aromatic ring reactant.
(b) Employing a Lewis acid catalyst at high temperatures.
(c) Adding a deactivating group (electron-withdrawing substituent) to the aromatic ring.
(d) Increasing the reaction time will ensure complete conversion.
The decomposition of H O follows first-order kinetics. If the initial concentration of H O is doubled, what
happens to the half-life (t / )?
(a) Remains the same.
(b) Decreases by half.
(c) Increases by a factor of two.
(d) Requires additional information about the rate constant (k).
Chlorine (Cl) has a higher electron gain enthalpy (ΔEg) compared to Fluorine (F). How does this relate to
their oxidizing nature?
(a) Higher ΔEg in Cl indicates stronger oxidizing ability.
(b) Lower ΔEg in F signifies a greater tendency to gain electrons (oxidize).
(c) ΔEg has no bearing on the oxidizing power of these elements.
(d) Both Cl and F have similar oxidizing tendencies.
An exothermic reaction exhibits a higher rate constant (k) at higher temperatures. Explain how this
observation relates to the activation energy (Ea) of the reaction.
(a) Higher temperatures provide more energy to overcome the existing Ea.
(b) The reaction becomes endothermic at high temperatures, lowering Ea.
(c) Rate constant (k) is independent of temperature and activation energy.
(d) Increased temperature reduces the need for activating collisions.
A catalyst increases the rate of a reaction by lowering the activation energy. However, it does not affect
the overall ΔH (enthalpy change) of the reaction. Explain this observation.
(a) The catalyst participates in the reaction and gets consumed.
(b) Catalysts provide an alternate reaction pathway with lower Ea.
(c) A catalyst increases the temperature, leading to a higher rate constant.
(d) Catalysts change the stability of products, altering the ΔH.
In a first-order reaction, the half-life is inversely proportional to the initial concentration ([A ]). If the initial
concentration is tripled, how much will the time required for 75% decomposition change?
(a) Increase by a factor of 3.
(b) Decrease by a factor of 3.
(c) Increase by a factor of 2.
(d) Decrease by a factor of 2.
The rate constant (k) of a chemical reaction typically increases with temperature. However, some reactions
exhibit a decrease in rate at very high temperatures. Explain this observation.
(a) High temperatures can deactivate catalysts required for the reaction.
(b) The pre-exponential factor (A) in the Arrhenius equation becomes negative at high temperatures.
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