Atoms and reactions — Advanced

Score: 0 / 10

Level 3: Advanced

Evaluate, justify, synthesise, propose — combine ideas, judge claims and methods (senior secondary style).

1. Evaluate a claim: We doubled the temperature so the rate doubled, therefore temperature is the only factor that matters.

   A)Sound — a linear link to temperature proves no other variable was changing in the setupB)Reasonable if the students also doubled concentration without noticingC)Too simplistic — other factors (concentration, surface area, catalyst) can dominate; need controlled comparisonsD)Invalid only because reaction rates are independent of temperature in most reactions

2. Justify storing reactive metals under oil or inert conditions:

   A)Reduces contact with air/water that could trigger unwanted oxidation or reactionsB)Keeps the metal cooler so its atoms vibrate less and cannot reactC)Prevents contact with oil-soluble impurities that would otherwise catalyse the metalD)Forces the metal into a passive oxide layer by excluding nitrogen only

3. A student proposes only melting point to identify an unknown compound in a mixture. The best critique is:

   A)Sharp melting is enough identification even inside a mixture containing soluble impuritiesB)Different substances can have similar melting points; combine tests (solubility, spectra, etc.) and separationC)Melting point is unreliable for ionic compounds but definitive for molecular onesD)Mixtures always melt over a range, so a single reading rules out a pure compound

4. Synthesise: choosing a greener route might involve:

   A)Choosing harsher oxidants to drive every step to completion in one passB)Maximising by-product mass so waste streams are easy to filterC)Avoiding catalysts to keep the pathway simple and avoid recovery stepsD)Catalysts, milder conditions, or fewer hazardous by-products where possible

5. Evaluate “Because the reaction is exothermic, it must be instantaneous.”

   A)True for all combustionB)True — heat always means fast kineticsC)Misleading — thermodynamics (exo/endo) does not fix rate; catalysts, temperature and pathway matterD)False — exothermic reactions never release energy

6. Justify using relative atomic mass on the periodic table while isotopes exist:

   A)The tabulated value is a weighted average over naturally occurring isotope abundancesB)Every atom of an element has the same mass numberC)Isotopes are ignored in chemistryD)Atomic mass equals neutron count only

7. Critique balancing $\text{CH}_4 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$ without tracking energy and conditions:

   A)The equation is invalid because methane is organicB)Stoichiometry shows mole ratios, but complete combustion needs sufficient O₂, mixing and ignition — side products possible if notC)Water cannot form from combustionD)Coefficients forbid checking atom counts

8. Propose why nanoparticle catalysts might outperform bulk metal in some lab demos:

   A)They have lower atomic numberB)They remove activation energy entirely for all reactionsC)They prevent any collisionsD)Far higher surface area per mass exposes more active sites

9. Synthesise periodic reactivity of metals with electron loss trends:

   A)Metals never lose electronsB)Reactivity is unrelated to electron structureC)Down a group, outer electrons are farther from the nucleus; alkali metals tend to become more reactive down the group (general trend)D)Across a period, metals always become more reactive without exception

10. A student says rate law can always be read directly from the balanced equation. The best response is:

    A)Rate orders are experimental; stoichiometry alone does not guarantee molecularity in complex mechanismsB)Always true for gasesC)False — equations never balanceD)True only for decomposition

← Back to hub