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OpenStem
@openstem · Joined Jul 2026
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Quiz5 questions
A sample transmits 10% of the incident light (T = 0.10). What is its absorbance?
AA = 1.0BA = 0.10CA = 10DA = 0.90
Chemistry · L4 · Colorimetry & Beer-Lambert Law — 5 Q
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Chemistry · L4 · Colorimetry & Beer-Lambert Law — 5 QQuiz5 questions
At the same temperature, why does a lighter gas molecule move faster, on average, than a heavier one?
ABecause all gases have the same average kinetic energy at a given T, so a smaller mass requires a larger average speed to keep KE = (1/2)mv^2 the sameBBecause lighter molecules experience less gravityCBecause heavier molecules always have lower temperatureDThere is no such relationship — speed is unrelated to mass
Chemistry · L4 · Effusion, Diffusion & Graham's Law — 5 Q
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Chemistry · L4 · Effusion, Diffusion & Graham's Law — 5 QQuiz5 questions
Which equilibrium expression is correctly written for CaCO3(s) <=> CaO(s) + CO2(g)?
AKc = [CO2]BKc = [CaO][CO2] / [CaCO3]CKc = [CaCO3] / ([CaO][CO2])DKc = [CaO] / [CaCO3]
Chemistry · L4 · Heterogeneous Equilibria & Kp — 5 Q
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Chemistry · L4 · Heterogeneous Equilibria & Kp — 5 QQuiz5 questions
What is the molecular ion produced by electron impact (EI) ionization, and what is distinctive about it?
AM+., an odd-electron radical cation whose m/z equals the compound's nominal molecular weightBM2+, an even-electron dicationCM-, an anion formed by electron captureDA neutral fragment with no charge at all
Chemistry · L4 · Mass Spectrometry Fragmentation — 5 Q
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Chemistry · L4 · Mass Spectrometry Fragmentation — 5 QQuiz5 questions
In retrosynthetic analysis, which direction does the disconnection arrow point, and why?
AFrom the complex target toward simpler precursors, since the analysis works backward from the targetBFrom simple starting materials toward the target, identical to a forward reaction arrowCIt has no defined directionDFrom the solvent toward the product
Chemistry · L4 · Organic Synthesis Routes — 5 Q
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Chemistry · L4 · Organic Synthesis Routes — 5 QQuiz5 questions
In the half-reaction method for acidic solution, in what order should O and H be balanced relative to balancing non-O/H atoms?
ABalance non-O/H atoms first, then O with H2O, then H with H+BBalance H with H+ first, then O, then all other atomsCBalance charge first, before any atomsDThe order does not matter
Chemistry · L4 · Balancing Redox Equations & Redox Titrations — 5 Q
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Chemistry · L4 · Balancing Redox Equations & Redox Titrations — 5 QQuiz5 questions
How much heat is required to raise 200.0 g of water from 20.0 °C to 45.0 °C? (c_water = 4.18 J/(g·°C))
A20 900 JB16 720 JC8360 JD37 620 J
Chemistry · L4 · Calorimetry Calculations — 5 Q
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Chemistry · L4 · Calorimetry Calculations — 5 QQuiz5 questions
What two problems does a molecular docking program solve for each candidate compound?
AOnly the ligand's molecular weight and solubilityBSearch (finding the ligand's binding pose) and scoring (estimating that pose's binding affinity)COnly synthesizing the compound computationallyDOnly predicting the compound's toxicity
Chemistry · L5 · Computational Docking & Drug Design
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Chemistry · L5 · Computational Docking & Drug DesignQuiz6 questions
Identify the substituent on the ring below, and predict where a second electrophile would attack.
AAn amino group — activating, so the ring is attacked at the ortho and para positionsBA nitro group — deactivating, so the ring is attacked at the meta positionCA nitro group — activating, so the ring is attacked at the ortho and para positionsDA hydroxyl group — deactivating, so the ring is attacked at the meta position
Chemistry · L4 · Reading Structures, Schemes & Calibration Curves — 6 Q
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Chemistry · L4 · Reading Structures, Schemes & Calibration Curves — 6 QQuiz4 questions
According to Hückel's rule, which of the following is aromatic?
ACyclooctatetraene (8 π electrons)BCyclopentadienyl cation (4 π electrons)CNaphthalene (10 π electrons)DCyclobutadiene (4 π electrons)
Chemistry · L5 · Quantum Chemistry & Spectroscopy
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Chemistry · L5 · Quantum Chemistry & SpectroscopyQuiz4 questions
Which condition most strongly favours an SN2 pathway over SN1?
ATertiary substrate in a polar protic solventBPrimary substrate, strong nucleophile, polar aprotic solventCSecondary substrate, weak nucleophile, aqueous EtOHDTertiary substrate, strong nucleophile, non-polar solvent
Chemistry · L5 · Organic Mechanisms & Kinetics
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Chemistry · L5 · Organic Mechanisms & KineticsQuiz5 questions
According to the Boltzmann distribution, what happens to the population of a higher-energy state relative to a lower one as temperature decreases?
AIt increases, approaching equal population with the lower stateBIt decreases exponentially, concentrating population in the lower stateCIt stays exactly constant, independent of temperatureDIt oscillates periodically with 1/T
Chemistry · L5 · Statistical Thermodynamics
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Chemistry · L5 · Statistical ThermodynamicsQuiz6 questions
According to the spectrochemical series, which of these ligands produces the largest crystal field splitting energy Δo?
AI⁻BH₂OCNH₃DCN⁻
Chemistry · L5 · Ligand Field Theory
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Chemistry · L5 · Ligand Field TheoryQuiz6 questions
What is the total electron count of Fe(CO)5 by the 18-electron rule?
A16B17C18D20
Chemistry · L5 · Organometallic Chemistry & Catalytic Cycles
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Chemistry · L5 · Organometallic Chemistry & Catalytic CyclesQuiz6 questions
What does the Hartree-Fock method approximate the many-electron wavefunction as?
AA single Slater determinant of one-electron orbitals, solved self-consistentlyBAn exact sum over every possible electron configurationCA single electron density function of 3 coordinatesDA classical trajectory of point charges
Chemistry · L5 · Computational Chemistry & DFT Basics
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Chemistry · L5 · Computational Chemistry & DFT BasicsQuiz5 questions
In Marcus theory, which factor captures the energy cost of distorting both the electron-transfer species and the surrounding solvent to the geometry needed for transfer?
AThe driving force, ΔG°BThe reorganization energy, λCThe electronic coupling, H_ABDThe Arrhenius activation energy, Eₐ
Chemistry · L5 · Marcus Theory & Electron Transfer Kinetics
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Chemistry · L5 · Marcus Theory & Electron Transfer KineticsQuiz6 questions
What is the key physical difference between the glass transition (Tg) and the melting temperature (Tm) of a polymer?
ATg applies to the crystalline fraction; Tm applies to the whole sampleBTg is a first-order transition with latent heat; Tm has noneCTg marks when amorphous chain segments gain enough mobility for cooperative motion; Tm is the first-order melting of the crystalline fraction onlyDTg and Tm are two names for the same transition
Chemistry · L5 · Polymer Science & Materials Chemistry — 6 Q
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Chemistry · L5 · Polymer Science & Materials Chemistry — 6 QQuiz6 questions
Why does 2D NMR spectroscopy become necessary for larger, more complex molecules?
A1D spectra lose signal intensity for larger moleculesB1D spectra become too crowded and overlapping to assign individual signals reliablyC1D NMR cannot detect ¹³C nuclei at allD2D NMR always requires less instrument time than 1D NMR
Chemistry · L5 · Advanced NMR: 2D Techniques & Coupling Analysis
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Chemistry · L5 · Advanced NMR: 2D Techniques & Coupling AnalysisQuiz5 questions
Which process is a nanosecond-scale, spin-allowed S1 → S0 emission?
AFluorescenceBPhosphorescenceCIntersystem crossingDInternal conversion to the ground state
Chemistry · L5 · Photochemistry
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Chemistry · L5 · PhotochemistryQuiz6 questions
Which term describes a host cavity already pre-shaped to match its guest before binding, minimizing the energetic and entropic cost of complex formation?
APreorganizationBTautomerismCRacemizationDIsomerism
Chemistry · L5 · Supramolecular Chemistry
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Chemistry · L5 · Supramolecular ChemistryQuiz6 questions
What does the E-factor measure, and why can atom economy alone miss what it captures?
AE-factor = mass of waste / mass of product, measured from the real executed process (solvents, purification losses, byproducts); atom economy is a purely stoichiometric prediction from the balanced equation before the reaction is runBE-factor and atom economy are just two names for the same calculationCE-factor measures only the byproduct mass predicted by stoichiometry, while atom economy accounts for solventsDAtom economy is always numerically higher than the E-factor for the same reaction, so the two cannot be compared
Chemistry · L5 · Green Chemistry — Sustainable Catalysis — 6 Q
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Chemistry · L5 · Green Chemistry — Sustainable Catalysis — 6 QQuiz6 questions
In the enzyme mechanism E + S ⇌(k1,k−1) ES →(k2) E + P, applying the steady-state approximation to [ES] gives which equation?
Ak_1[\text{E}][\text{S}] = k_{-1}[\text{ES}] + k_2[\text{ES}]Bk_1[\text{E}][\text{S}] = k_{-1}[\text{ES}] - k_2[\text{ES}]Ck_1[\text{E}][\text{S}] + k_{-1}[\text{ES}] = k_2[\text{ES}]D[\text{ES}] = [\text{E}][\text{S}]
Chemistry · L5 · Enzyme Kinetics
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Chemistry · L5 · Enzyme KineticsQuiz6 questions
Which of the following is a core assumption of the Langmuir adsorption model?
AThe surface has a fixed number of identical, non-interacting sites, each holding at most one adsorbed moleculeBAdsorbed molecules can stack indefinitely in multiple layersCAdsorption sites interact strongly with their neighbours, favouring clusteringDThe number of available sites increases as pressure increases
Chemistry · L5 · Surface Chemistry and Adsorption
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Chemistry · L5 · Surface Chemistry and AdsorptionQuiz6 questions
What does the third law of thermodynamics state?
AThe entropy of any substance is zero at room temperatureBThe entropy of a perfect, pure crystalline substance approaches zero as temperature approaches absolute zeroCEnthalpy and entropy become equal at absolute zeroDNo process can reach absolute zero in a finite number of steps
Chemistry · L5 · The Third Law and Absolute Entropy
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Chemistry · L5 · The Third Law and Absolute EntropyQuiz6 questions
What is the CFSE (in units of Δo) for an octahedral d³ ion such as [Cr(H₂O)₆]³⁺?
A−0.6ΔoB−1.2ΔoC−1.8ΔoD0Δo
Chemistry · L5 · Crystal Field Stabilization Energy
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Chemistry · L5 · Crystal Field Stabilization EnergyQuiz6 questions
Why does conventional free-radical polymerization typically give a broad molecular-weight distribution (high PDI)?
ABecause the monomer used is always a mixture of different structuresBBecause initiation and irreversible termination both occur randomly at scattered times throughout the reaction, so chains grow for very different lengths of timeCBecause free-radical polymerization always uses a metal catalyst that broadens PDIDBecause free-radical chains cannot propagate past a fixed maximum length
Chemistry · L5 · Controlled and Living Polymerization — 5 Q
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Chemistry · L5 · Controlled and Living Polymerization — 5 QQuiz6 questions
What does the quadrant model describe in chiral bisphosphine hydrogenation catalysis?
AA chiral bidentate ligand's bulky groups create two blocked and two open quadrants around the metal, forcing the prochiral substrate to bind in only one orientationBThe metal cycles through four different oxidation states during one catalytic turnoverCFour different achiral phosphine ligands compete for the same coordination siteDThe substrate is hydrogenated equally on all four possible approach faces
Chemistry · L5 · Asymmetric Catalysis Mechanisms — 6 Q
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Chemistry · L5 · Asymmetric Catalysis Mechanisms — 6 QQuiz5 questions
A Schottky defect in an ionic crystal consists of what?
AA single cation vacancy, with no accompanying anion vacancyBA matched pair of vacancies — one cation site and one anion site both left emptyCA cation displaced into an interstitial site, leaving a vacancy behindDAn extra ion squeezed into an interstitial gap with no vacancy created
Chemistry · L5 · Crystal Defects and Semiconductors
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Chemistry · L5 · Crystal Defects and SemiconductorsQuiz6 questions
A mass spectrum shows a molecular-ion cluster with M at 100% intensity and M+2 at approximately 33% intensity, with no significant M+4 peak. Which halogen is most likely present?
AFluorineBChlorineCBromineDIodine
Chemistry · L5 · Advanced Mass Spectrometry
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Chemistry · L5 · Advanced Mass SpectrometryQuiz6 questions
What has to be true of a semiconductor particle's size, relative to the exciton Bohr radius, for quantum confinement effects to become significant?
AThe particle must be much larger than the exciton Bohr radiusBThe particle must be smaller than the exciton Bohr radiusCThe particle's size relative to the exciton Bohr radius makes no differenceDThe particle must exactly equal the exciton Bohr radius, and no other size works
Chemistry · L5 · Nanomaterials and Quantum Confinement
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Chemistry · L5 · Nanomaterials and Quantum Confinement