periodicity + reactivity Flashcards
carbonate test
react with acid to form CO2 gas - add nitric acid and bubble gas through limewater
sulfate test
barium sulfate = insoluble
barium chloride/nitrate added - white ppt = positive
which substance should you use in the sulphate test if you want to do the halide test after it?
barium nitrate
basis for halide test
silver halides are insoluble
halide test
- add silver nitrate to aqueous halide solution
- ppt = positive
- add aqueous ammonia to test solubility to tell colours apart
colour of chloride ppt
white
solubility of chloride ppt in NH3
soluble in DILUTE
colour of bromide ppt
cream
colour of iodide ppt
yellow
solubility of bromide ppt in NH3
soluble in CONCENTRATED
solubility of iodide ppt in NH3
insoluble in CONCENTRATED
sequence of qualitative analysis tests
1) Carbonate
2) Sulfate
3) Halide
test for ammonium ion
- NaOH added to solution
- ammonia gas produced (v soluble In water)
- mixture warmed and gas released
- test pH with moist pH paper - turn BLUE
can ammonium nitrate conduct electricity?
yes
benefits of using chlorine in water purification
- kills bateria
disadvantages of using chlorine in water purification (3)
- chlorine is toxic
- is respiratory irritant
- can react with hydrocarbons forming chlorinated hydrocarbons - cause cancer
why do halogen boiling points increase down the group [3]
- London forces (dipole-dipole interactions increase)
- because number of electrons increase
- therefore more energy to break intermolecular forces
why is it important that a colorimeter is calibrated before use? how would you calibrate it [3]
- to provide reference values
- record values given by colorimeter for known concentrations
- plot graph so unknown concentrations can be worked out from a given reading from colorimeter
melting point trend across p 2+3
– why?
increase between 1 and 4
decreases 4-5
low from 5-0
– because change from giant to simple molecular structures
group 2 elements act as
REDUCING AGENTS
solubility of group 2 oxides down the group
- pH?
increases,
increases - alkalinity increases
uses of group 2 compounds as bases
- Ca(OH)2 added to field to raise soil pH
- antacids
boiling point trends down halogens
- why?
INCREASES
- more electrons, more London forces, more energy required to break bonds
benefits of chlorine in water treatment (1)
kills bacteria
disadvantages of chlorine in water treatment (3)
- toxic gas
- react w organic haloalkanes to produce chlorinated hydrocarbons - carcinogens
- respiratory irritant
halide test
+ aq. silver nitrate
= 3 coloured ppts
