Chapter 15 - Reversible Reaction

Question 1

Reversible reactions

Irreversible: Most chemical reaction are considered this (products wont readily change back into reactants)

Reversible - Can get product back to reactant
E.g heating and hydrating copper sulphate
Heating = change from blue to anhydrous white > Adding water turns white crystals blue again (hydrating them)

Answer 1

Open, closed, Isolated

Isolated - Flask > neither matter nor energy can escape due to vacuum

Closed - Water bottle > Matter cant escape but energy can

Open - Coffee cup > Allows energy and matter out

Question 2

Dynamic Equilibrium

Equilibrium: Unchanging amount

Dynamic: reaction is still occurring

Rate of forwards reaction = rate of backwards reaction

Answer 2

Le chateliers principle

If a dynamic equilibrium is disturbed by changing conditions, the reaction moves to counteract the change

Things that influence a reaction: Inc/Dec the conc of substances;Changing pressure; Changing temp; changing a catalyst

Effect of catalyst: - will speed up both sides of a reaction - position of equilibrium doesn’t change

Question 3

Adding/taking away substances

• By adding to one side, the reaction will add to the other side
• By subbing one side the reaction will produce more on that side

Answer 3

A+2B <> C + D

Adding A causes position of equilibrium to shift right to produce more C + D favouring a forwards reaction

Removing C+D causes the position of equilibrium to shift right to produce more C + D
Favouring a forwards reaction

Question 4

Effect of pressure

Inc pressure > side with less molecules gets produced more

Dec pressure > Side with more molecules get produced

Answer 4

Effect of temp

If Temp Inc - favours endothermic reaction to bring temp down

If Temp Dec - Favours exothermic reaction to bring temp back up

Question 5

Manufacturing chemicals

The Haber process

3H2 + N2 <> 2NH3 forward reaction = exo

Production of ammonia:
Made from nitrogen from air and hydrogen made from methane and water
Conditions - 450* - too low = useless
- 200atm - too high = expensive
- Iron catalyst

Answer 5

Compromise Conditions:
Means they are not too high (too expensive) but not too low (bad production)

If Temp Inc: Production lessens (see le chataliers principle

If pressure Inc: More ammonia production (see le chataliers principle)

Question 6

Manufacturing of H2SO4

Uses - Fertilisers, manufacturing detergents (soaps hand washes) and paints 
Conditions: 450*
                    1-2 ATM
                     V2O3 catalyst 
Stage 1 - S + O2 > SO2
Stage 2 - 2SO2 + O2 <> 2SO3
Stage 3 ----------
Stage 4 - SO3 + H2SO4 > H2S2O7
Stage 5 - H20 + H2S2O7 > 2H2SO4

Answer 6

Contact process

Stage 1: Sulfur is burned in air to make sulfur dioxide Gas
Stage 2: Sulfur dioxide is mixed with more air to make sulfur trioxide - reversible reaction
Stage 3: Gases are passed through layers of vanadium oxide catalyst at 450*
Stage 4: Sulfur trioxide added to concentration Sulphuric acid to make fuming sulphuric acid
Stage 5: Water is added to oleum to make 98% sulphuric acid