Chapter 8 - Reactivity Trends Flashcards
Group 2, The halogens and Quantitative analysis.
What is a reducing agent?
A species that donates it’s electrons to another species, thereby reducing that species.
Which group are reducing agents commonly found?
Group 2
(Be, Mg, Ca, St, Br)
What is the trend in reactivity down group 2?
Reactivity increases. (This is because the further away an electron is from the nucleus)
Explain the trend of reactivity down group 2
Increased atomic radius and shielding effect so ionisation energies decrease. Therefore it’s easier to lose electrons.
What are the products of a group 2 element reacting with water? metal + water = ?
metal + water = Metal hydroxide and hydrogen
What is the product of a group 2 element reacting with oxygen? metal + oxygen = ?
metal + oxygen = Metal oxide
group 2 metal oxide + water = ?
group 2 oxide + water = metal hydroxide
What is the trend of solubility down group 2?
Increases
Explain the trend of solubility down group 2
Down the group, the solution has a greater concentration of OH-.
Given that group 2 oxides, hydroxides and carbonates neutralise acids, what can they be referred to as?
Bases
Given that most group 2 oxides, hydroxides and carbonates are soluble in water, what are they also besides bases?
Alkalis
What is the use of calcium hydroxide in agriculture?
Increases the pH of acidic soils.
Ca(OH)(2) + 2H+ -> Ca2+ + 2H(2)O
How are group 2 compounds used in medicine?
Used in indigestion tablets as antacids, often a suspension of a metal hydroxide in water.
What is another name for group 2?
Alkaline Earth Metals
What is another name for group 7?
Halogens
What is the trend in boiling point down group 7?
Increases
Explain the trend in boiling point down group 7
More electrons,
Stronger induced dipole-dipole forces,
More energy to break intermolecular forces,
Boiling point increases.
What is the trend in reactivity down group 7?
Reactivity decreases
Explain the trend in reactivity down group 7
Atomic radius increases, More inner shells, Shielding increases, Nuclear attraction decreases, Reactivity decreases.
What do more reactive halogens do to less reactive halide ions?
Displace them
What can displacement reactions be used to identify?
Which halide is present in solution.
Which compound is used to test for halides?
Silver nitrate solution. AgNO3
How can the results for a halide test be further tested?
Solubility in ammonia solution
What is disproportionation?
A redox reaction in which the same element is both oxidised and reduced.
Describe the test for carbonates
Carbonates react with acids to form carbon dioxide gas.
Add dilute nitric acid to testing solution. If bubbles observed could be a carbonate. To prove its CO(2), bubble gas through lime water, limewater turns cloudy (milky) .
Describe the test for sulphates
the test for sulphates is to add Aqueous barium nitrate to the solution. If a white precipitate forms, there is a sulphate.
In the halide tests, what happens to chloride with silver nitrate and then ammonia
chlorine
Silver nitrate - white precipitate
Ammonia - soluble in dilute ammonia
In the halide tests, what happens to bromide with silver nitrate and then ammonia
Silver nitrate - cream precipitate
Ammonia - soluble in concentrated ammonia
In the halide tests, what happens to iodide with silver nitrate and then ammonia
(AgNO3) Silver nitrate - yellow precipitate
Ammonia - insoluble in concentrated ammonia
What is the correct order for these anion tests?
Carbonate test, sulphate test, halide test
C.S.H
Why is this the correct order for anion tests carbonate, sulphate, halide?
Carbonates also form a white precipitate in the sulphate test but not vice versa.
Carbonates and sulphates form precipitates with silver nitrate.
CSH
Describe the test for ammonium ions
Add aqueous NaOH (sodium hydroxide) to the solution,
Ammonia gas is produced,
Can be detected with moist indicator paper as it will turn blue.
the test for halide ions table?
