Module 5 Flashcards
Reversible reactions
forward and reverse reactions are possible- drawn with a arrow pointing in both directions
What are the properties of reversible reactions?
- reverse thermodynamic properties
- values of enthalpy, entropy and gibbs free energy would be the negative or the reverse
What are the types of equilibrium a reaction can have?
Dynamic equilibrium and static equilibrium
Are all reversible reactions in dynamic equilibrium
No. Dynamic equilibrium is only`a type of reversible reaction
Investigation- reversibility of cobalt(II) chloride hexahydrate
What materials are involved in this experiment?
- 5g of cobalt (II) chloride hexahydrate
- Evaporating dish
- Gauze mat
- Bunsen burner
- Demineralised water
Investigation- reversibility of cobalt(II) chloride hexahydrate
What is the method of the experiment? Draw experimental set-up.
- Add 5g of cobalt(II) chloride hexahydrate in an evaporating dish and set it is on top of a gauze mat
- Gently heat the cobalt (II) chloride hexahydrate with Bunsen burner and observe for any colour changes
- When there are no colour changes after 5 minutes, add 5 mL of demineralised water to re-dissolve the salt
- Evaporate the solution and observe for changes
Investigation- reversibility of cobalt (II) chloride hexahydrate
Why was demineralised water added to the salt after evaporation?
By adding water to the evaporated solution, we test the reversibility of cobalt(II) chloride hexahydrate
Investigation- reversibility of cobalt (II) chloride hexahydrate
Observations are?
- Cobalt (II) chloride hexahydrate is a dark pink colour
- Heating cobalt (II) chloride hexahydrate causes the substance to turn into a purple colour (cobalt (II) chloride dihydrate)
- Heating cobalt (II) chloride dihydrate causes it to become sky blue (cobalt (II) chloride anhydrous)
- The colour of cobalt(II) chloride dihydrate is a fleeting colour where it quickly appears and disappears
- By adding water, the solution becomes dark pink
- When reheating the solution, the observations are recalled to be the same
What is the colour of cobalt (II) chloride hexahydrate?
Pink
What s the colour of cobalt chloride dihydrate?
Purple
What form of cobalt (II) chloride is sky blue?
Anhydrous
What happens when hexahydrate is heated?
The waters of crystallisation are gradually vaporised
Investigation of the reversibility of cobalt (II) chloride hexahydrate
Why does the appearance of the solution remain the same despite the form of cobalt(II) chloride.
Despite the water crystallisation number, as cobalt (II) chloride is dissolved the hydration spheres formed around them is exactly the same- the number of crystallisation numbers don’t have an effect.
Investigating the reversibility of the combustion of metals-
Materials?
- magnesium strip
- steel wool
- crucible and lid
- bunsen burner
- tripod and pipeclay triangle
- test tube
- Ice bath
Investigating the reversibility of the combustion of metals- Method . Draw a diagram.
- Place pipeclay triangle above tripod( with the heat proof mat underneath)
- Place bunsen burner underneath the tripod
- Place crucible on top of pipeclay triangle with the lid slightly opened
- Place magnesium strp within the crucible
- Ignite flame on bunsen burner and open gas pipe
- Observe any changes to the magnesium strip
- Collect remaining solid and place within a test tube in an ice bath
- Observe any changes
Investigating the reversibility of the combustion of metals
What colour of the solid formed by heating the magnesium in the crucible?
White solid- magnesium oxide
Red solid- iron (III) oxide
Investigating the reversibility of the combustion of metals- Why is the white solid placed in the ice bath?
By placing it in an ice bath, we test the reversibility by attempting to reverse the original change of heating it.
Investigating the reversibility of the combustion of metals- What colour is formed when steel wool is heated?
Reddish brown solid is formed as steel wool is heated.
What is dynamic equilibrium?
The rates of conversion in the forwards reaction- reactants to products- and the reverse reaction- products to reactants- are equal and non-zero
What is static equilibrium
The rates of forward and reverse reactions are equal and practically zero. The reaction doesn’t proceed after equilibrium has been reached.
mainly due to high activation energies
The movement of particles in the dynamic and static equilibrium.
Dynamic equilibrium
- movement of particles in the forward and reverse reactions
- constant microscopic flux
- no macroscopic observations
Static equilibrium- properties
Static
- No movement of particles in the forward and reverse reactions
- No microscopic flux
- No macroscopic observations
Dynamic equilibrium- reaction rate
- Rate of reaction depends on concentration of the reactants
- forward reaction is initially fast as the concentration of reactants is large at first
- slow reverse reaction rate
- As the reactants are consumed within the reaction and the concentration of the products increase, the forward rate of reaction rate decreases and the reverse rate of reaction decreases
- Dynamic equilibrium is reached when the reverse rate of reaction equals the forward rate of reaction
Concentration of dynamic and static equilibrium
Dynamic and Static equilibrium have constant concentrations
