Chapter 8 - Reactivity trends Flashcards
What is the name given to Group 2 elements?
Alkaline earth metals
Why are Group 2 elements called reducing agents?
Each metal atom is oxidised, losing 2 electrons which will be gained by another species (which is reduced). Therefore it is called a reducing agent as it has reduced another species
What are the products of the group 2 elements reacting with oxygen?
Group 2 elements react with oxygen to form a metal oxide with the general formula of MO. It is a redox reaction
What are the products of the Group 2 elements reacting with water?
Group 2 elements react with water to form and alkaline hydroxide with the general formula M(OH)2 and hydrogen gas. It is a redox reaction
What are the products of the Group 2 elements reacting with dilute acids?
Group 2 elements react with acids to form a salt and hydrogen. It is a redox reaction
Why do Group 2 elements become more reactive and stronger reducing agents down the group?
Atoms of Group 2 react by losing electrons to form +2 ions. Ionisation energy decreases down the group because the nuclear attraction on outer electrons decreases as a result of increasing atomic radius and increasing shielding. Ionisation energy decreases down the group.
How do the Group 2 oxides react with water?
Group 2 oxides react with water to release hydroxide ions (OH-) and forming alkaline solutions of the metal hydroxide
How does the solubility of the hydroxides in water change down Group 2?
Solubility increases down the group
What does the change in solubility in Group 2 hydroxides mean for the resulting solutions?
Solubility increases down the group, so the resulting solutions contain more OH- ions and are more alkaline (have a higher pH)
How are Group 2 compounds used in agriculture?
Calcium hydroxide is added to fields as lime by farmers to increase the pH of acidic soil. This neutralises the acid in the soil to form neutral water.
How are group 2 compounds used in medicine?
Group 2 bases are often used as antacids for treating acid indigestion. Many indigestion tablets use magnesium and calcium carbonates to neutralise the hydrochloric acid in your stomach
How and why does the boiling point change down Group 7?
Boiling point increases down Group 7
This is because there are more electrons, therefore stronger London forces and more energy required to break the intermolecular forces.
Why are halogens oxidising agents?
Halogen atoms gain an electron from another species (so are reduced), and are therefore called oxidising agents as they have oxidised another species
How and why does reactivity change down Group 7?
Reactivity decreases down Group 7
This is because atomic radius increases down the group, and there are more inner shells so shielding increases. There is less nuclear attraction to capture an electron from another species.
How do the halogens take part in displacement reactions?
A more reactive halogen will displace a less reactive one. If the halogen added to a halide solution is more reactive, then the halogen will take the place of the halide in solution.
What colours are chlorine, bromine and iodine in solution?
Chlorine - pale green
Bromine - orange
Iodine - brown
What colours are chlorine, bromine and iodine in cyclohexane solution?
Chlorine - pale green
Bromine - orange
Iodine - violet
What is a disproportionation reaction?
A redox reaction in which the same element is both oxidised and reduced
What is the equation for chlorine reacting with water?
Cl2 (aq) + H2O (l) → HClO (aq) + HCl (aq)
How is chlorine used in water purification?
The products of chlorine’s reaction with water are chloric acid and hydrochloric acid, which kill bacteria. Chloric acid also acts as a weak bleach.
What is the equation for the reaction between chlorine and cold, dilute aqueous sodium hydroxide?
Cl2 (aq) + 2NaOH (aq) → NaClO (aq) + NaCl (aq) + H2O (l)
Why must reactions with chlorine be performed in a fume cupboard?
Chlorine is a toxic gas, and is a respiratory irritant in small concentrations
Why must water be filtered before being purified with chlorine?
Chlorine can react with organic hydrocarbons such as methane, formed from decaying vegatations. Chlorinated hydrocarbons are formed, which are carcinogenic (supsected of causing cancer).
How can you test for a carbonate (CO3 2-) ion?
- Add dilute nitric acid to unknown solution/solid
- If you see bubbles, unknown could be carbonate
- To prove gas is CO2, bubble through limewater, will turn it cloudy
