1.1. Chemical Equilibrium

distinguish between physical and chemical changes

Physical changes:

• change in state, size or shape

• no new substance is form

• usually reversible

Chemical changes:

• new substance is formed with different properties

• only some are reversible

Distinguish between a closed and open system and give an example

Closed:

• matter does not enter or leave, only energy

• E.g. heating water in closed test tube (heat escape but not water vapour)

Open:

• matter AND energy can be exchanged with surrounding

• E.g. boiling water in an open pot (water vapour escapes)

What is chemical equilibrium? What happens to concentration here? Does it occur in closed or open systems? What does it look like?

When the rate of the forward reaction = the rate of the reverse reaction

• concentration can differ but is CONSTANT

• ONLY closed systems

• Constant appearance and properties stable

What is activation energy? E^lower A. How do you read an Activation energy graph?

Activation energy is the minimum amount of energy required for the reactant particles to collide/break bonds and start the reaction.

• higher activation energy for both forward and reverse means it’s unlikely to occur

• lower E^lower A for both means it’s easier to occur

How to read graph:

• forward takes from reactants up to peak

• reverse takes from products up to peak

Which one is forward favoured/towards the right? which one is reverse favoured/towards the left? Justify.

The right picture is forward favoured as there is more products at equilibrium and hence the reaction tends to produce more products.

The left picture is reverse favoured as there is more reactants at eq. and hence reaction tends to produce more reactants.

Distinguish static and dynamic equilibrium

Dynamic:

• both forward and reverse reactions are occurring

Static:

• forward and recerse reactions are NOT occurring (Irreversible, rate of reaction = 0 for both)

what is the formula for concentration when given volume of gas and volume of container?

What is the enthalpy for endothermic and exothermic reaction like?

Endothermic:

• Heat is absorbed therefore the enthalpy is POSITIVE because heat is consumed from surrounding

Exothermic:

• Heat is released therefore the enthalpy is NEGATIVE because heat is released out into surrounding