CHEMISTRY

Unit 05: Energetics

5.0 Predicts the stability of chemical systems and feasibility of  conversions by investigating associated changes in enthalpy and entropy

5.1 Explores concepts related to enthalpy.

Describes the extensive and intensive properties.

Defines the terms system, surrounding, boundary, closed system, open system and isolated system.

States the standard states of pure substances and solutions.

Defines the terms state of a system and a state function.

Describes enthalpy as a function of state or thermodynamic property but not heat.

States that Integral value for ΔH reported in kJ or per unit extent of reaction (kJ mol^-1).

Calculates the enthalpy changes associated with process using. ΔH = H (final) –H (initial)

5.2 Defines the enthalpy changes and calculates enthalpy changes associated with a given conversion.

Calculates enthalpy changes using

Q = mcΔT

Explains the endothermic and exothermic reactions using energy diagram.

Defines enthalpy changes and standard enthalpy changes given in the syllabus.

States Hess Law

Calculates enthalpy changes using

enthalpy diagrams

thermochemical or thermodynamic cycles

Only using formation enthalpies as well as only using bond dissociation enthalpies separately.

Determines experimentally the enthalpy of neutralization of acids and bases

Tests the validity of Hess law by preparing 250cm³  1moldm^-3 NaCl using two methods

5.3 Calculates the lattice enthalpy or enthalpy of  formation of an ionic compound using Born-Haber cycles.

Defines the enthalpy changes used to develop the Born Haber cycle.

Develops the Born – Haber cycle related to lattice enthalpy.

Calculates the standard lattice enthalpy using the Born – Haber cycle.

Explains the variation of electron gain enthalpies of elements of second and third periods.

5.4 Predicts the spontaneity of chemical reactions.

Explains the terms entropy (S) and entropy changes(ΔS)

Explains Gibbs energy (G) and Gibbs energy change (ΔG)

States that S and G are state functions.

Calculates ΔS and ΔG using

ΔS = S_(products) – S_(reactants)

ΔG= G _(products) – G _(reactants)

Energy cycle

Explains the terms ΔG⁰ and ΔS⁰

States the relationship among ΔG, ΔH and ΔS.

States the relationship among G⁰, H⁰ and S⁰.

Predicts the spontaneity of a reaction or an event occurring under constant pressure and temperature using ΔG,.

States that ΔG and ΔS are reported as a integral quantity per extent of a reaction. (kJ mol^-1)

ΔG (kJ mol^-1) ,ΔS (kJK^-1 mol^-1) or ΔG (kJ ), ΔS (JK^-1 )

Calculates the problems based on standard values, ΔG⁰ , ΔH⁰  and ΔS⁰.

Forecasts the feasibility of a reaction using the value of ΔG