§-Unit

Unit 3: How can design and innovation help to optimise chemical processes?

8 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

What are the current and future options for supplying energy?

redox reactions with reference to the electrochemical series, including the writing of balanced half-equations and overall ionic equations, the identification of oxidants and reductants, the prediction of spontaneous reactions, and the use of standard electrode potentials at 25°C

Redox reactions and the electrochemical series. Covers oxidation and reduction in terms of electron transfer, writing and balancing half-equations, identifying oxidants and reductants, and using standard electrode potentials to predict spontaneous reactions.

11 min read →

the writing of thermochemical equations to represent the energy released or absorbed in physical and chemical changes, including the sign convention for ΔH for exothermic and endothermic reactions, and the use of ΔH values with mole ratios to calculate the energy released or absorbed

Thermochemical equations. Covers the meaning of ΔH, the sign convention for exothermic and endothermic reactions, the use of states in the equation, and how to scale ΔH using mole ratios.

10 min read →

the use of solution calorimetry and bomb calorimetry to measure the energy released by chemical reactions, including the use of the specific heat capacity of water and q = mcΔT to calculate the energy released by combustion of fuels and the molar enthalpy of combustion

Calorimetry. Covers solution and bomb calorimetry, the use of q = mcΔT with the specific heat capacity of water, calibration factors, calculation of molar enthalpy of combustion, and the common sources of error.

11 min read →

the design and operation of galvanic cells, including primary cells, secondary (rechargeable) cells and fuel cells, with reference to the role of anode, cathode, electrolyte, salt bridge and external circuit, and the calculation of cell EMF (E°_cell) from standard electrode potentials at 25°C

Galvanic cells. Covers the components of a galvanic cell, the distinction between primary, secondary and fuel cells, the direction of electron and ion flow, and the calculation of E°_cell from standard electrode potentials.

11 min read →

the definition of a fuel, the distinction between fossil fuels (coal, crude oil, natural gas) and biofuels (bioethanol, biodiesel, biogas), and the comparison of fuels with reference to energy content per unit mass (in kJ g^-1) and energy density per unit volume (in kJ L^-1) and renewability

Fuels. Covers the definition of a fuel, the fossil fuel vs biofuel distinction, energy content (kJ g^-1) vs energy density (kJ L^-1), and how to compare fuels on energy values and renewability.

10 min read →

How can the yield of a chemical product be optimised?

the concept of dynamic equilibrium for reversible reactions, the equilibrium law expression and equilibrium constant Kc (including the meaning of Q vs Kc and the units of Kc), and the qualitative application of Le Chatelier's principle to predict the effect on equilibrium of changes in concentration, gas pressure (volume), temperature and the addition of a catalyst

Equilibrium. Covers dynamic equilibrium, the equilibrium expression and Kc, the role of the reaction quotient Q, and Le Chatelier's principle for changes in concentration, pressure, temperature, and the addition of a catalyst.

12 min read →

the design and operation of electrolytic cells for the commercial production of chemicals, including comparison with galvanic cells, the polarity of electrodes in each, the difference between molten and aqueous electrolysis, and the application of Faraday's laws using Q = It and n(e) = Q/F to calculate the mass of substance produced or consumed

Electrolytic cells. Covers electrolysis of molten and aqueous electrolytes, the comparison with galvanic cells, electrode polarity, and quantitative calculations using Faraday's laws (Q = It and n(e) = Q/F).

11 min read →

the factors that affect the rate of a chemical reaction (concentration, surface area, temperature and the presence of a catalyst) explained using collision theory and the Maxwell-Boltzmann distribution of kinetic energies, including the representation of these effects on energy profile diagrams

Rate of reaction. Covers collision theory, the four factors that affect rate (concentration, surface area, temperature, catalyst), the Maxwell-Boltzmann distribution, activation energy, and energy profile diagrams.

11 min read →