Testing for Ions Flashcards
what are the precautions to be taken when working with a toxic substance
use a fume cupboard
wear protective gloves
what are the precautions to be taken when working with a corrosive substance
wear safety goggles
wear protective gloves
what are the precautions to be taken when working with an irritant
wear safety glasses
wear protective gloves
use a dust mask
what is the test for chlorine
test the gas with damp blue litmus paper, it first turns red and then bleaches
what is the test for ammonia
test the gas with damp red litmus paper, it turns blue
what are the different ways of collecting gases
collected over water (if the gas is insoluble)
collected by upward delivery (if the gas soluble in water and less dense than air)
collected by downward delivery (if the gas is soluble in water and denser than air0
how do you measure the volume of a gas
using a gas syringe
how do you carry out a flame test
clean a platinum wire loop using HCL.
Pick up a small amount of the solid using the wire loop
Heat the solid in the edge of a blue bunsen flame/roaring flame
observe and the record the colour of the flame
what are the different colours of positive ions in a flame test
lithium
sodium
potassium
calcium
copper
lithium - red
sodium - yellow
potassium - lilac
calcium - orange red
copper - blue green
why is it difficult to identify 2 different ions in a compound using a flame test
the two colours would mix together
what are the advantages of instrumental methods of analysis over flame tests
more sensitive
more accurate
more rapid
what can a flame photometer do
identify the metal ions in a substance and measure the concentrations of metal ions
how is a metal ion in an unknown solution identified
matching its spectrum to the spectrum from a known metal ion
why is distilled water used to make the standard solutions rather than tap water
tap water contains dissolved metal ions which may interfere with the results
distilled water does not contain metal ions
how is a calibration curve for the concentration of K+ ions produced
using standard solutions of K+ ions and a flame photometer
what are the strengths of flame tests
they are simple to carry out
do not need expensive equipment
what are the weaknesses of flame tests
a large amount of sample is needed
cannot identify different metal ions in a mixture
cannot determine the conc of metal ions in a sample
what are the strengths of a flame photometer
small amount of sample is needed / more sensitive
can identify different metal ions in a substance
accurately determine the conc of metal ions in a sample
how can you identify metal ions using metal hydroxide solution
a few drops of metal hydroxide solution are added to the solution containing the metal ion
a precipitate of the metal hydroxide is formed
the colour of the precipitate can be used to identify the metal ion
what coloured precipitates are formed when sodium hydroxide solution is added to aluminium, calcium, copper, iron 2+ , iron 3+
aluminium - white precipitate
calcium - white precipitate
copper - blue precipitate
iron 2+ - green precipitate
iron 3+ - brown precipitate
what happens when you add excess sodium hydroxide solution to aluminium ions
the white precipitate dissolves to form a colourless solution
what is the test for ammonium ions
add sodium hydroxide solution to the solution and warm
ammonia gas is produced when the mixture is warmed
test the gas with damp red litmus paper
it goes from red to blue which confirms ammonia
what is the test for carbonate ions
add dilute HCL to the substance and test the gas produced with limewater.
Fizzing is observed and the limewater turns cloudy
what is the test for chloride/bromide/iodide ions
add a few drops of dilute nitric acid (to remove any carbonate ions that may be present) then add silver nitrate solution
what colour precipitates do chloride/bromide/iodide ions form
chloride - white precipitate
bromide - cream precipitate
iodide - yellow precipitate
what is the test for sulfate ions
add a few drops of dilute HCL then add barium chloride solution, a white precipitate of barium sulfate is formed
