Chapter 8 - Reactivity Trends Flashcards
Explain the trend of reactivity down Group 2?
Group 2 elements react by losing or sharing electrons.
Reactivity increases down the group due to a decrease in first and second ionisation energies. This is due to:
- Increasing atomic radius
- Increasing electron shielding
- Less attraction between the nucleus and the outer electrons.
- Electrons are lost more easily.
What is a reducing agent?
A substance which reduces other things but are themselves oxidised.
Vice versa for oxidising agents.
Metal + Oxygen →
Metal + Oxygen → Metal Oxide
Metal + Water →
Metal + Water → Metal Hydroxide + Hydrogen
Metal Oxide + Water →
Metal Oxide + Water → Alkaline solution
Metal Hydroxide + Water →
Metal Hydroxide + Water → Precipitate OR Alkaline solution
Group 2 hydroxides are only slightly soluble in water and much of the hydroxide product may form a precipitate instead of an alkaline solution.
What is the trend of solubility of Group 2 hydroxides down Group 2?
The solubility of Group 2 hydroxides in water increases down the group. The solutions become more alkaline because they contain more OH- (aq) ions.
What are the uses of Group 2 bases?
- Calcium hydroxide is used in agriculture to neutralise acid soils
- Magnesium hydroxide and calcium carbonate are used as ‘antacids’ to neutralise acids that cause indigestion.
Explain the trend of boiling point down the halogen group in terms of intermolecular forces.
The boiling points of the halogens increase down the group.
- The halogens exist as diatomic molecules (e.g. Cl2, Br2)
- In the solid state, the halogens form simple molecular lattices, with weak London forces between the halogen molecules.
- Down the group, the halogen molecules contain more electrons, increasing the strength of the London forces.
- More energy is required to break the London forces, increasing the boiling point.
What is the trend of reactivity down the halogen group?
Halogens react by gaining or sharing an electron.
Reactivity decreases down the halogen group:
- Increased number of shells so increased atomic radius and shielding
- The attraction between the nucleus and the outer electrons decreases
- The attraction for an external electron decreases.
What is the colour of chlorine as an aqueous solution and when mixed with cyclohexane?
Aqueous solution - Pale green
+ cyclohexane - Pale green
What is the colour of bromine as an aqueous solution and when mixed with cyclohexane?
Aqueous solution - Orange
+ cyclohexane - Orange
What is the colour of iodine as an aqueous solution and when mixed with cyclohexane?
Aqueous solution - Brown
+ cyclohexane - Violet
How can displacement reactions between halogens and aqueous halides be used to show the trend of reactivity of halogens down the group?
What is the trend of reactivity down the halogen group?
Reactivity of halogens decreases down the group.
- A solution of each halogen is mixed with solutions of the other halides
- If a reaction takes place, the halogen (higher in the group) oxidises the halide ion, removing an electron from each halide ion.
At RTP, fluorine is…
…a yellow gas.
