Flashcards in Chapter 8 Deck (47)
List 2 group 2 elements
Are group 2 elements oxidising or reducing agents?
How can group 2 elements act as reducing agents?
Can lose 2 electrons to become oxidised (2+ ions) when reducing another species
Metal + O2 --> ?
Metal + H2O --> ? + ?
Metal hydroxide + H2
Metal + acid --> ? + ?
Salt + H2
Write an equation for the reaction of magnesium with oxygen
2 Mg + O2 --> 2 MgO
Write an equation for the reaction between magnesium and water
Mg + 2 H2O --> Mg(OH)2 + H2
Write an equation for the reaction between magnesium and hydrochloric acid
Mg + 2 HCl --> MgCl2 + H2
Describe the trend in reactivity as you go down Group 2
Ionisation energy decreases due to increased shielding / increased atomic radius
Decreased nuclear attraction between the outer electrons and the nucleus
Describe the trend in solubility (of hydroxides) as you go down Group 2
Solubility increases because solutions contain more OH-, increasing the pH and alkalinity
Give 2 uses of Group 2 compounds?
What group 2 compound can be used in agriculture?
Ca(OH)2 added to fields to increase the pH of acidic soils
What group 2 compound can be used in medicine?
Used in medicines for heartburn and indigestion
Describe the trend in boiling point as you go down the halogen group
Boiling point increases
Stronger London forces
More energy required to overcome these forces
Describe the trend in reactivity as you go down the halogen group
Atomic radius/shielding increases
Less nuclear attraction to capture an electron from another species
Hence, reactivity decreases
What type of reaction shows that the reactivity of the halogens decreases down the group?
Halogen-halide displacement reactions
Describe how a halogen-halide displacement reaction would be carried out
1) Solution of each halogen added to (aq) solutions of the other halides
2) Reaction takes place and solution changes colour
What is the most reactive halogen?
Reacts with both Br- and I-
What is the least reactive halogen?
Doesn't react with either Cl- or Br-
What colour is seen in a solution of bromine in water?
What colour is seen in a solution of iodine in water? (before cyclohexane is added)
What colour is a solution of iodine in water, after cyclohexane is added?
What can you add to solutions of iodine and bromine in water to tell the 2 colours apart?
Are the halogens polar or non-polar?
What is a disproportionation reaction?
A redox reaction in which the same element is both oxidised and reduced
Write an equation for the reaction of chlorine with water (disproportionation reaction)
Cl2 + H2O --> HClO + HCl
Write an equation for the reaction of chlorine with cold, dilute NaOH (disproportionation reaction)
Cl2 + 2 NaOH --> NaClO + NaCl + H2O
What is a use of chlorine?
What is an implication of using chlorine to purify water?
Chlorine is a respiratory irritant
What 3 tests are involved in qualitative analysis of anions, in order?
Describe the carbonate test
1) Add dilute acid (HNO3)
2) Effervescence indicates carbonate ions
What test can you use to check that the gas produced in the carbonate test is CO2?
Lime water test
CO2 turns lime water cloudy
Write an equation for the reaction between sodium carbonate and nitric acid
Na2CO3 + HNO3 --> NaNO3 + CO2 + H2O
Describe the sulfate test
1) Add a solution containing Ba 2+ ions
2) White precipitate indicates sulfate
Write an equation for the reaction between Barium ions and sulfate ions
Ba 2+ + SO4 2- --> BaSO4 (s)
What indicates the presence of sulfate ions?
Describe the halide test
1) Add solution containing Ag+ ions (AgNO3)
2) Precipitates of silver halides form
3) Add NH3 (aq) to test the solubility of precipitates formed
What colour precipitate is silver chloride?
What colour precipitate is silver bromide?
What colour precipitate is silver iodide?
What conditions is silver chloride soluble in?
Soluble in dilute NH3 (aq)
What conditions is silver bromide soluble in?
Soluble in conc. NH3 (aq)
What conditions is silver iodide soluble in?
Insoluble in conc. NH3 (aq)
Describe the test for cations (NH4+)
1) Add NaOH
2) Ammonia gas is released
3) Turns indicator blue because ammonia is alkaline
Write the equation for the reaction between NH4+ and OH-
NH4+ + OH- --> NH3 + H2O