1. Structure & Bonding
The bond type formed by sharing electron pairs between non-metals; common examples include H2 and Cl2
Covalent bonding
The constant equal to particles per mole.
Avogadro’s constant (Avogadro’s number)
Chromatography value calculated as distance spot moved divided by distance solvent front moved.
Rf value
The reaction type where an acid reacts with a base to form a salt and water.
Neutralisation (acid-base) reaction
A polymer category that softens on heating and can be remoulded and recycled—typically linear chains.
Thermoplastic (linear addition polymer, e.g., HDPE)
The intermolecular force responsible for unusually high boiling point and surface tension in water; occurs when hydrogen is bonded to N, O, or F.
Hydrogen bonding
The term for the mass of one mole of a compound, usually expressed in g mol−1.
Molar mass (or relative molecular mass expressed as g mol−1)
A titration indicator change occurs at the endpoint; name one common acid-base indicator used for strong acid vs strong base titrations.
Phenolphthalein (or methyl orange — accept common indicators with context)
The balanced half-reaction for the oxidation of zinc metal to zinc ion.
Zn→ 〖Zn〗^(2+)+ 2e^-
Term describing an economy where materials are reused, recycled, or repurposed to minimise waste.
Circular economy
The macroscopic property of metals (e.g., conductivity, malleability) explained by delocalised electrons in a lattice.
Metallic bonding
If you have 0.50 mol of NaCl (molar mass 58.44 g mol−1), the mass of NaCl is approximately — give the calculation.
29.22g
In colorimetry, the calibration curve plots this on the y-axis versus concentration on the x-axis.
Absorbance
Predict the product when aqueous solutions of BaCl2 and Na2SO4 are mixed; name whether a precipitate forms.
Barium sulfate BaSO4 precipitate forms; sodium chloride stays aqueous.
The polymerisation type where alkene monomers add to form a polymer without elimination of small molecules.
Addition polymerisation
Two allotropes of carbon with very different properties: one is extremely hard and an electrical insulator; the other conducts electricity along planes.
Diamond (hard, insulator) and graphite (conducts along planes)
A gas collected at SLC has volume 24.8 L and contains 1.0 mol of gas. State the molar volume at SLC and relate it to the result.
Molar volume at SLC ≈ 24.8g; one mole occupies ~24.8 L under SLC.
Give one reason a titration result might be systematically low (underestimate concentration of analyte).
Possible answers: overshooting endpoint removal of some titrant before final reading, using an indicator that changes late (or early) — or not rinsing burette correctly, air bubble in burette — accept plausible systematic error reasons.
Use Brønsted-Lowry definitions: identify the conjugate acid of NH3 and the conjugate base of H2O
Conjugate acid of NH3 is NH4+; conjugate base of H2O is OH-.
Name one biodegradable polymer derived from plant-based resources used as a compostable alternative to fossil-fuel plastics.
Polylactic acid (PLA) or Bio-PE (if specifying bio-based polyethene) — accept appropriate bioplastic.
Explain why MgO has a much higher melting point than NaCl, using lattice energy and ionic charge considerations.
MgO has higher melting point because Mg2+ and O2− have greater charges and smaller ionic radii than Na+ and Cl−, leading to a much larger lattice energy and stronger ionic attraction, so more energy is required to separate ions.
A hydrated salt sample weighing 2.758 g is heated to give an anhydrous mass of 1.404 g. The anhydrous formula unit mass is 158.0 g mol−1. Determine the formula’s mole ratio of water to salt and give the empirical formula of the hydrate.
Mass of water lost = 2.758-1.404=1.354 g
Moles of anhydrous salt = 1.404/158.0=0.00889 mol
Moles of water = 1.354/18.02=0.0751 mol
Ratio water : salt = 0.0751:0.00889 ≈ 8.45:1 ≈ 8:1 → empirical hydrate formula: salt · 8H_2 O (accept 8 waters; show rounding justification)
Explain how you would design a calibration curve for determining phosphate concentration by colorimetry, including blank, standards range, and use of the curve to find an unknown.
Prepare a reagent blank (no phosphate) to zero the instrument; prepare a series of standard phosphate solutions spanning expected concentration range; measure absorbance of blank and standards in cuvettes; plot absorbance vs concentration and determine best-fit line (slope, intercept); measure unknown’s absorbance (run in same conditions), subtract blank if needed, use calibration equation to calculate concentration; account for dilutions and report mg L−1 with units and uncertainty.
Write full equations AgNO3 with KCl, and explain any solubility rules used
Solubility rule: Nitrate salts and potassium salts are soluble (spectators); silver chloride is insoluble → precipitate.
AgNO3 + KCl -> AgCl (s) + KNO3
Compare mechanical recycling vs chemical recycling of plastics and discuss one environmental advantage and one limitation of each.