(3.17-3.22C) Reversible reactions + equilibria

What is a reversible reaction?

The products react with each other and convert back to the reactions.

A reaction which can travel both ways.

What is the sign for reversible reactions?

⇌

Describe the thermal decomposition of ammonium chloride.

• Heating NH₄Cl → NH3 + HCL

• The gases formed recombine as they cool

• forming the white solid again

Describe the dehydration of hydrated copper (II) sulfate.

• CuSO4×5H20 → CuSO4 + 5H20

• It can go both ways.

What is dynamic equilibrium?

In a closed system,

• the concentrations of reactants and products will reach and stay at a constant

• the reaction occurs at a equal rate in both directions

Why does a catalyst not affect rate in a reversible reaction?

It speeds up the backwards and forwards reaction by the same amount

so rate remains the same.

How can the position of equilibrium shift?

If a change is made to the conditions of a system in equilibrium

usually in temperature/pressure

the system shifts to oppose the change

If the temperature of a system in equilibrium decreases…

shift towards the exothermic reactions- to give out more heat.

If the pressure of a system in equilibrium increases…

shift towards reaction that gives least molecules- to decrease pressure