Reactivity Trends Flashcards
What are group 2 metals called?
Alkaline Earth Metals
What are group 2 metals found as on Earth?
Stable compounds such as calcium carbonate
How does the electron configuration of Group 2 metals differ from that of a noble gas?
Two more electrons than the nearest noble gas
What is the most common type of reaction of group 2 elements?
Redox
What happens to a group 2 metal during a redox reaction?
Oxidised
Loses 2 electrons
Becomes a 2+ ion
Is group 2 an oxidising agent or reducing agent? Why?
Reducing agent- reduces another species by being oxidised
What is the reaction of a group 2 metal and oxygen?
Group 2 metal + oxygen = Metal Oxide
What happens when magnesium burns?
Magnesium burns with a bright light
What happens when a group 2 metal reacts with water?
Metal + Water = Metal hydroxide + Hydrogen
What happens to reactivity of group 2 metals with water down the group?
Reactivity increases down the group
What happens when a group 2 metal reacts with acid?
Metal + Acid = Salt + Hydrogen
What happens to reactivity in group 2 metals? Why?
Increases
Requires 2 ionisation energies.
Ionisation energy decreases because of greater shielding and atomic radii.
What is the reaction of group 2 oxides with water?
Group 2 oxide + water= metal hydroxide
Explain trend in solubility of hydroxides
Increases down the group
Resulting solutions contain more OH- ions
Explain trend in alkalinity of hydroxides
Solubility increases
More OH- ions
Increase in pH
Increase in alkalinity
What is the pH of magnesium hydroxide?
10
What is the pH of barium hydroxide?
13
How are group 2 compounds used in agriculture?
Ca(OH)2 are added to fields as lime to increase pH of acidic sols
What is the equation of group 2 compounds in agriculture?
Ca(OH)2 (s) + 2H+(aq) = Ca 2+(aq) + 2H20(l)
Which 2 group 2 compounds are used in medicine?
CaCO3
Mg(OH)2
Give the 2 equations of group 2 compound s in medicine
Mg(OH)2 +2HCl = MgCl2 + 2H20
CaCO3+ 2HCl = CaCl2 +H20 + CO2
Where are halogens found?
Sea Water
Potassium and Sodium deposits
What is the appearance and state of fluorine at room temperature and pressure?
Pale yellow gas
What is the appearance and state of chlorine at room temperature and pressure?
Pale green gas
What is the appearance and state of bromine at room temperature and pressure?
Red brown liquid
What is the appearance and state of iodine at room temperature and pressure?
Shiny grey-black solid
What is the appearance and state of astatine at room temperature and pressure?
Never been seen
Explain the trend in boiling points of halogens
More electrons
Stronger London forces
More energy required to break intermolecular forces
Boiling point increases
How does the electron configuration of halogens link to that of a noble gas?
One less electron than the nearest noble gas
Is a halogen a reducing or oxidising agent?
Oxidising agent, induces oxidation in another species by being reduced
What do displacement reactions show?
Reactivity of halogens decreases down the group
What colour are chlorine, iodine and bromine in water?
Chlorine- pale green
Bromine- orange
Iodine- brown
What colour are chlorine, iodine and bromine in cyclohexane?
Chlorine- pale green
Bromine- orange
Iodine- violet
Explain the trend in reactivity of halogens
Atomic Radii increases
Greater Shielding
Less nuclear attraction to capture electron from another species
Reactivity decreases
What is a disproportionation reaction?
A redox reaction in which the same element is both oxidised and reduced
What are 2 examples of disproportionation reactions?
Chlorine with water
Chlorine with cold, dilute sodium hydroxide
Write reaction of chlorine with water
Cl2 (aq) +H20 (l) = HClO (aq) + HCl
Write reaction of chlorine with cold dilute sodium hydroxide
Cl2 (aq) +2NaOH (aq) = NaClO +NaCl + H20
What are the negatives to using chlorine?
Toxic gas
Respiratory irritant
Can be chlorinated hydrocarbons- which are cancer causing
Describe process of carbonate test
Add dilute nitric acid to test tube
See bubbles = carbonate
How do you test for CO2?
Add saturated aqueous solution of calcium hydroxide
Describe sulfate test
Add Ba2+ ions in the form of barium chloride or nitrate
Barium Sulfate forms which is an insoluble white precipitate if sulfate is present
Describe halide test
Add aqueous silver nitrate
Different colour precipitates form
What is the equation for the halide test?
Ag +(aq) + X-(aq) = AgX(s)
What colours are the halide precipitates?
Chloride- white precipitate
Bromide- cream precipitate
Iodide- yellow precipitate
How does solubility of the halides vary with aqueous ammonia?
Chloride- soluble in dilute NH3
Bromide- soluble in conc. NH3
Iodide- insoluble in conc. NH3
What is the correct order of test for anions?
Carbonates
Sulfates
Halides
Why do carbonates have to be tested for before sulfates?
BaCO3 also forms a solid white precipitate
How do you test a mixture of chemicals?
Carry out tests in same sequence and on the same solution
How do you test for the ammonium ion?
Add aqueous sodium hydroxide
Ammonia gas produced
Warm
Test gas with indicator paper
