Unit 11 Enthalpy

System

chemicals/reacting molecules

Enthalpy (H)

heat energy stored in chemical system

Exothermic
> bond __; energy __; surroundings __heat (more/less)
> __ve ΔH as p__ energy < r__ energy
> e.g. n__, c__, r__

making, released, more, -ve, product, reactant, neutralisation, combustion, respiration

Endothermic
> bond __; energy __; surroundings __heat (more/less)
> __ve ΔH as r__ energy < p__ energy
> e.g. p__, l__, ice packs

breaking, absorbed, less, +ve, reactant, product, photosynthesis, lightning

Activation energy

min amt of energy needed for successful collision

What energy change is this?

exothermic

What energy change is this?

endothermic

Y axis?

energy

X axis?

progress of reaction

e__, __

exo, reactants

e__, __ e__

exo, activation energy

e__, __ve Δ__

exo, -ve, H

e__, __

endo, reactants

e__, __ e__

endo, activation energy

e__, __ve Δ__

endo, +ve, H

e__, __

endo, products

Energy change is measured via a

calorimeter

To find ΔH,
1. use _ = __Δ_
2. ΔH = (_/1000) / _

Q, mcT, Q, n

ΔH unit

kJ/mol

Why Q/1000?

J to kJ

Bond energy

amt of energy needed to break 1 mole of bonds in a molecule to form indiv atoms

↑b__ e__ = s__ c__ bond & ↑energy needed to b__ it & separate atom

bond energy, str covalent, break

fill in the blank

reactant, product