Unit 2: Molecular interactions and reactions
7 dot points across 2 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.
Topic 2: Aqueous solutions and acidity
- Calculate the concentration of aqueous solutions in mol/L, g/L, percent by mass or volume, and parts per million (ppm), and apply dilution and stoichiometric relationships to solutions
A focused answer to the QCE Chemistry Unit 2 dot point on solution concentration. Defines mol/L, g/L, percent and ppm; works through interconversions; applies the dilution formula c_1 V_1 = c_2 V_2; and links to solution stoichiometry calculations for reactions in aqueous solution.
8 min answer → - Describe acids and bases qualitatively, distinguish between strong and weak acids using the extent of ionisation, calculate the pH of strong acid and base solutions, and write balanced equations for the reactions of acids with metals, carbonates and hydroxides
A focused answer to the QCE Chemistry Unit 2 dot point on acidity. Defines acids and bases qualitatively, introduces the pH scale and Kw, distinguishes strong from weak acids by extent of ionisation, calculates pH of strong acid and base solutions, and writes balanced equations for acid reactions with active metals, metal carbonates and metal hydroxides.
9 min answer → - Apply solubility rules to predict whether ionic compounds are soluble in water, predict precipitation reactions between aqueous solutions, and write balanced full and net ionic equations including spectator ions
A focused answer to the QCE Chemistry Unit 2 dot point on solubility and precipitation. Lists the QCAA solubility rules for common ionic compounds, walks through predicting whether a precipitation reaction occurs when two aqueous solutions are mixed, and shows how to write balanced molecular, complete ionic and net ionic equations.
8 min answer → - Explain the properties of water as a solvent in terms of its polarity and hydrogen bonding, and describe the dissolution of ionic and polar molecular substances in water
A focused answer to the QCE Chemistry Unit 2 dot point on water as a solvent. Explains why water's bent shape and O-H bonds give it a permanent dipole and extensive hydrogen bonding, then walks through ion-dipole solvation of NaCl, hydrogen-bonding solvation of ethanol, and the "like dissolves like" rule with worked exceptions.
8 min answer →
Topic 1: Intermolecular forces and gases
- Apply stoichiometric relationships to reactions involving gases, calculating volumes, masses or amounts of reactants and products using the mole ratio and molar volume or ideal gas equation
A focused answer to the QCE Chemistry Unit 2 dot point on gas stoichiometry. Sets out the four-step mole map for reactions with gas reactants or products, applies the molar volume at SLC and the ideal gas equation, and works through limiting-reactant and percent-yield calculations of the type QCAA poses in EA short response.
8 min answer → - Apply the ideal gas equation (PV = nRT) and the concept of molar volume at standard conditions to calculate amounts of gases under varying conditions of temperature and pressure
A focused answer to the QCE Chemistry Unit 2 dot point on PV = nRT. Sets out the ideal gas equation with QCAA's preferred units, derives molar volume at standard laboratory conditions (24.79 L/mol at SLC), and works through calculations linking pressure, volume, temperature and amount of gas.
8 min answer → - Explain the behaviour of gases using the kinetic theory of matter, and apply Boyle's law, Charles's law and the combined gas law to predict the effect of changing pressure, volume and temperature
A focused answer to the QCE Chemistry Unit 2 dot point on gas behaviour. States the assumptions of the kinetic theory of gases, derives Boyle's, Charles's and Gay-Lussac's laws qualitatively from particle behaviour, and works through combined gas law problems of the kind QCAA poses in EA Paper 1.
8 min answer →