Chapter 8 - Reactivity trends Flashcards
What is the most common reaction in group two metals?
redox reactions
What do the group two elements react with oxygen to form?
metal oxides
What do the group two elements react with water to form?
alkaline hydroxide x(OH)2
what does a metal and an acid produce?
salt and hydrogen
how does reactivity of group two change down the group?
it increases
why does the reactivity increase down group two?
the attraction between the nucleus and the outer electrons decreases, increasing atomic radius and increase in shielding
how does the solubility,ph and alkalinity of the group two hydroxides change down the group?
all increases
What is the test for carbonates?
Add dilute nitric acid
positive test = fizzing
What is the test for sulfates?
Add aqueous barium nitrate or barium chloride
positive test = white precipitate
what is the test for halides?
add aqueous silver nitrate
bromide = cream
chloride = white
iodide = yellow
how can you tell the halides apart?
Add aqueous ammonia
chloride = soluble in dilute NH3
bromide = soluble in conc NH3
iodide = insoluble in NH3
What is the sequence of the tests?
1) carbonates
2) sulfates
3) halides
why is this sequence of tests important?
- sulfate not halide ions fizz with dilute acid
- barium carbonate forms a white precipitate
- silver sulfate and silver carbonate form precipitates
What is the test for ammonium ions?
add aqueous sodium hydroxide and warm the solution
positive test = moist pH indicator will turn blue
At RTP what do the halogens exist as?
diatomic molecules
describe and explain the change in boiling point of the halogens
increases down the group, due to more electrons which increase the strength of London forces
what are the most common type of reaction of the halogens
redox
what colour does chlorine, bromine and iodide then in water?
Cl - pale green
Br - orange
I - brown
which halogen changes colour in cyclohexane and to what colour?
iodine turns violet
describe and explain the change in ionisation energy in ionisation energy of the halogens?
ionisation energy increases because atomic radius increases, shielding increases and there is less nuclear attraction to capture an electron from another species
what is disproportionation?
a redox reaction in which the same element is both oxidised and reduced
