rate of chemical reactions

What is delta U?

How does it vary?

U - internal energy

Sum of all kinetic energy + potential energies

Delta U changes related to heat transfer and work done

What is enthalpy change?

How do you calculate delta H?

How to tell if reaction is endothermic or exothermic?

Enthalpy change - heat content of a system at constant pressure

Delta H = products - reactants

+ve = endothermic

-ve = exothermic

What is 1cal equal to in joules?

4.184J

Formula to calculate kinetic energy

K = Ae^EA/RT

Difference between homogeneous and heterogeneous catalysts?

Homogenous - catalyst in same phase as reactants

Heterogenous - catalyst in different phase as reactants

Describe heterogenous catalytic action

• Reactants adsorb (attach) to surface of catalyst

• Chemical bonds form between reactants and catalyst surface

• Products desorb (detach) from surface

• Catalyst regenerated

Describe homogenous catalytic action

• Catalyst forms complex with reactants

• This stabilises transition state and lowers activation energy

• Catalysed reaction takes place within complex

• This forms the products

• Products released from complex

• Catalyst regenerated