Topic 9: Reversible Reactions Flashcards
What is a reversible reaction?
A chemical change that is able to go backwards and forwards.
To represent a chemical process we use….?
Half arrows (=)
Experiment 1: Reversible reaction of acids and bases (3rd form)?
Change color of Phenolpholein by adding a few drops of NaOH (aq) to change the solution -> pink, then changing it back by adding HCL (aq) -> colorless
Experiment 2: Reversible reaction, testing for water?
CuSO4. 5H2O(s) ->(heat) (H2O)<- CuSO4(s) 5H2O
Experiment 3: Reversible reaction, of states of matter 3rd form - diffusion?
NH4Cl(s)(white solid) ->(heat) (cool)<- NH3(g) + HCL(g) (colorless)
What is Chemical Equilibrium?
This is “When the rate of forward reaction equals the rate of the backwards reaction”, the reaction is said to be in equilibrium.
What is a dynamic Equilibrium?
The type of equilibrium that occurs in chemical reactions is called a dynamic equilibrium.
How is the position of a Equilibrium changed?
The position of a equilibrium can be changed by altering the concentrations of reactants or products, temperature or pressure.
How can the concentration change the position of the equilibrium?
A + B == C + D
- If more A is added the equilibrium moves to the right to reduce the concentration of A.
How can the temperature change the position of the equilibrium?
A + B == C + D = Heat
- When the forward reaction is exothermic, if the temperature is increased, the equilibrium moves to the left to get rid of extra heat.
How can the pressure change the position of the equilibrium?
A(g) + B(g) == C(g)
- If the pressure is increased the equilibrium will move to the side with the fewest number of gas molecules to reduce the pressure.
The Chemical equilibrium rule?
A chemical equilibrium will move to counteract any change imposed on it.
Equation for the Bromine water experiment?
Br2(aq) +H2O(l) (yellow) == Br(aq) + OBr(aq) +H+(aq) (colorless)
Ammonia to ammonia chloride reaction?
ammonia (NH3(g)) + hydrogen chloride (HCL(g)) == ammonium chloride (NH4Cl(s).
Properties of Ammonia? NH3
- Colorless
- Colorless gas
- Vary soluble in water
- Pungent smell
- Gas at room temperature
- Base produces a solution of PH 10-11 when dissolved in water.
Ammonia is needed and the starting material for which products?
Nitric acid and ammonia nitrate (a fertilizer)
Main Equation for the Habour process?
nitrogen(N2(g)) + hydrogen(3H2(g)) == ammonia(2NH3(g))
The reaction for the Habour process is endothermic or exothermic?
Exothermic. (delta)H = -80kJmol-1
What is the catalyst used in the main Habour process reaction and why is it used?
- Iron catalyst is used.
- The catalyst (as with all reversible reactions) speeds up the reaction in both directions equally. So it simply reduces the amount of time taken to reach equilibrium.
To increase yield in the Main Habour Process reaction we could?
- Increase the pressure.
- reduce the temperature.
Conditions used for the main Habour Process reaction?
- Fe(Iron) Catalyst
- Pressure of 200 atm
- Temperature at 400o
Why is 450o used in Main Habour Process Reaction?
This is a compromise, it is hot enough to enable that reaction to take place quickly but not too hot to ensure the equilibrium sits for enough towards the product.
Why is 200atm used in Main Habour Process Reaction?
This is a compromise - it is high enough to increase yield but isent to expensive to maintain.
How is H2 created in the Habour Process?
Obtained by reacting steam with CH4
How is N2 created in the Habour Process?
Obtained for the air.
What form is ammonia collected in?
NH3 is cooled and collected as a liquid.
What does the statement ‘that a reaction has reached equilibrium’ mean?
Rate of forwards reaction = rate of backwards reaction.
Why is nitrogen important for plants?
Nitrogen is needed for proteins in the leaves and stalks.
If 80% of the air is nitrogen why can’t plants use this?
This is because it needs to be in the form of nitric acid. In a soluble form.
What happens when to much fertilizers are put on the fields?
Leaching occurs, Port from Biology, fertilizers in the water cause eutophication. Which causes other animals in the water to die.
What happens when nitrates are ingested?
- Stomach cancer
- Blue Baby Syndrome, not enough oxygen in the blood to aid respiration.
Step 1) in the production of H2SO4 - The Contact Process?
1) - Sulpher(S(s)) + Oxygen(O2(g)) = Sulpher dioxide(SO2(g))
Step 2) in the production of H2SO4 - The Contact Process?
2) Sulpher dioxide(2SO2(g)) + Oxygen(O2(g)) = Sulpher monoxide(2SO3(g))
- Temperature used : 440oC
- Catalyst used : V2O5
- High pressures are not needed as % conversion is already good enough.
Step 3) in the production of H2SO4 - The Contact Process?
3) Sulpher monoxide(SO3(g)) + Water(H2O(l)) = Sulpheric Acid(H2SO4(l)) - diluted and sent to customers.
Uses of Sulpheric Acid?
- Production of pharmaceuticals
- Production of Paint, fertilizers and explosives
- Used in metal treatment.
In the Habour Process what will be present in the equilibrium mixture with ammonia?
- Un-reacted gasses ie. H2 and N2 will be present when the gasses are cooled and condense to a liquid. They are recycled before reaching the iron catalyst.
In the Habour Process, How will the rate of reaction of nitrogen with hydrogen be affected by increasing the temperature.
The rate of reaction should increase because there is going to be more collisions between the atoms as the kinetic energy increases.
What is seen when excess ammonia solution is added gradually to copper (II) chloride solution. With formula.
light blue precipitate
darker blue solution
[Cu(NH3)4(H2O)2]2+
Nitric Acid?
Amonia?
HNO3
NH3
Explain why increasing the concentration of X has this effect on the rate of the reaction?
more particles
more successful collisions.
more frequently
