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PHYSICAL CHEM - ENERGETICS

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Total cards: 18•Content version: v4•Public deck•Updated: 8/1/2026

Card preview (18)

#1
Front (Question)

What is an endothermic reaction?

Back (Answer)

a reaction that absorbs heat energy from the surroundings

#2
Front (Question)

What is an exothermic reaction?

Back (Answer)

a reaction that releases heat energy into the surroundings

#3
Front (Question)

Is forming bonds exothermic/endothermic?

Back (Answer)

exothermic

#4
Front (Question)

Is breaking bonds exothermic/endothermic?

Back (Answer)

endothermic

#5
Front (Question)

What is enthalpy change (ΔH)?

Back (Answer)

the heat energy transferred in a reaction at constant pressure

#6
Front (Question)

Is the enthalpy change in endothermic reactions +ve/-ve?

Back (Answer)

ΔH is +ve

#7
Front (Question)

Is the enthalpy change in exothermic reactions +ve/-ve?

Back (Answer)

ΔH is -ve

#8
Front (Question)

What does ΔH° mean?

Back (Answer)

standard enthalpy change (reaction occurred under standard conditions)

#9
Front (Question)

What are standard conditions for a reaction?

Back (Answer)

• pressure = 100 kPa • stated temp (usually 298 K) • reactants and products in standard states

#10
Front (Question)

What is standard enthalpy change of formation (ΔfH°)?

Back (Answer)

the enthalpy change when 1 mole of a substance is formed from its constituent elements with all reactants and products in standard states under standard conditions

#11
Front (Question)

What is standard enthalpy change of combustion (ΔcH°)?

Back (Answer)

the enthalpy change when 1 mole of a substance is completely burned in O2 with all reactants and products in standard states under standard conditions

#12
Front (Question)

What is standard enthalpy change of neutralisation (ΔneutH°)?

Back (Answer)

the enthalpy change when 1 mole of water is formed in a reaction between an acid and an alkali under standard conditions

#13
Front (Question)

What is combustion calorimetry?

Back (Answer)

burning a sample and measuring temp rise of water to measure the amount of heat energy released

#14
Front (Question)

What is the equation that links heat energy required, mass, SHC and temp increase?

Back (Answer)

heat energy required (J) = mass (g) x SHC (J/g°C) x temp increase (°C/K) (q = mCΔT)

#15
Front (Question)

What is the equation that links enthalpy change, heat energy and moles?

Back (Answer)

enthalpy change (kJmol^-1) = heat energy (J) / moles (mol) (ΔH = q/n)

#16
Front (Question)

What is Hess’ law?

Back (Answer)

enthalpy change for a reaction is the same regardless of the route taken

#17
Front (Question)

What is mean bond enthalpy?

Back (Answer)

the enthalpy change required to break 1 mole of covalent bonds in the gas phase averaged over a range of compounds

#18
Front (Question)

Why is an average taken to measure bond enthalpies?

Back (Answer)

the exact value varies in different compounds