chemical analysis Flashcards
(33 cards)
what is a pure substance
one single substance containing one type of chemical
what is a mixture
more than one substance that are not chemically bonded
what is a formulation
a mixture that has been designed
what are the 6 methods of separation
filtration, evaporation, crystallisation, simple distillation, fractional distillation, chromatography
explain the separation process of filtration
solid from a liquid
use filter paper
explain the separation process of evaporation
separate a solid from a soluble
using heat
explain the separation process of crystallisation
producing solid crystals from a solution
use an evaporating dish
explain the separation process of simple distillation
separating a solvent from a solution
using a condensing tube
explain the separation process of fractional distillation
separate a solvent from a mixture of two or more liquids
condensing tube
explain the separation process of chromatography
separating disolved substances from one another
ink dyes
using chromatography paper
how does chromatography work
the solvent runs up the filter paper and the different chemicals separate out as they interact with the paper differently. some ink will bond more strongly than others
what is the calculation for an Rf value
distance travelled by substance divided by distance travelled by solvent
what are the four common gasses we test for
chlorine, oxygen, carbon dioxide, hydrogen
how do we test for chlorine and what are the results
place blue litmus paper in a test tube with the gas - if there is chlorine present the paper will turn from blue to red to white
how do we test for carbon dioxide and what are the results
bubble the gas through limewater - it will turn cloudy if co2 is present
how do we test for hydrogen and what are the results
a glowing splint into a test tube with the gas, if it makes a squeaky pop, hydrogen is present
how do we test for oxygen and what are the results
a glowing splint into a test tube with gas inside, if oxygen is present, splint will relight
when testing for ions why does the colour of the flame change
when heating, the electrons gain thermal energy, when these electrons return to lower energy levels, they emit the excessive energy as light
what are the flame colours for each ion testing
lithium - red
sodium - orange/yellow
potassium - purple
calcium - orange
copper - green
what are the negatives of using the normal flame testing method
hard to determine colour as they can be similar
samples can contain multiple metals and therefore colours mix
what is flame emission spectroscopy
a method of flame testing that uses a spectroscope which detects the individual wavelengths of light that is emoted
how do we identify the ion when using emission spectroscopy
the unique line spectrum that each metal ion produces
along with solving the problems that normal flame testing, what other benefit does flame spectroscopy have
the intensity of the lines on the wavelength depict how concentrated the ion is
how can we use flame emission spectroscopy to test for unknown ions
when looking at the line spectra for the unknown sample, we can compare it to know metal ions to see which ions are contained in the unknown sample
