Chemistry Reactivity 1.2 Energy Cycles

Enthalpy of formation

What is the product of burning of Hydrocarbon (compound made up of carbon and hydrogen) and oxygen

CO2 and H2O

A→B+C How to calculate the enthalpies change

A - (B+C) is the enthalpies of formation

2A→ B+3C

2A-(B+3C) is the enthalpies change. The cofficient must be taken into account.

What is the standard enthalpies change

enthalpy change that occurs when one mole of that substance is formed from its constituent elements, with all participating species in their standard states.

What is lattice enthalpies

Lattice enthalpy (AH}) is the standard enthalpy change that occurs when one mole of structural units of a solid lattice is separated into gaseous ions: M_X,(s) — aM"(g) + bX“(g)

What is MX(s) — M*(g) + X(g)

MX(s) = M(s) + 3 X,(@) = M(g) + 3 X,(8) = M'(@) + 3 X,(@) + & — M(g) + X(g) + & — M(g) + X (g)

Therefore AHP (MX) = -AHf’(MX, 8) + AHO(M) + AH)(M) + AHS:(X) +AH?, (X)