chemical analysis Flashcards
what is a pure substance
a single element or compounds that hasn’t been mixed with any other substances
what is a example of a pure substance
distilled water
how can you test how pure a substance is
chemically pure substances melt or boil and specific points
- you can test the purity of a substance by measuring its melting or boiling point and compare it to melt + boil point of the pure substance
- the closer the measured value is the purer it is
what are formulations
formulations are mixtures that have been prepared using a specific formula
formulations are made from..
precise amounts of different components and each component has a different function
what are some examples of things that would require a formulation
medicine
paints
cleaning agents
why would medicine need a formulation
- make sure drug goes to right part of body
- right concentration
- consumable
- has long enough shelf life
how can we test for chlorine
- put solution in a test tube
- put damp litmus paper into the solution
- if litmus paper turn white then chlorine is present as it bleaches the litmus paper
( the litmus paper may turn red before turning white)
how can we test for oxygen
- test tube containing oxygen
- put a glowing splint in the test tube
- the oxygen will relight the glowing splint if oxygen is present
how can we test for carbon dioxide
- put lime water into a test tube
- bubble carbon dioxide through it
- this will cause is the solution to turn cloudy and carbon dioxide is present
how can we test for hydrogen
- put hydrogen in a test tube
- hold a burning splint at the end of the test tube
- you will get a squeaky pop if hydrogen is present
what is chromatography
a chemical analysis to separate substances in a mixture
What is paper chromatography used for?
To separate a mixtures of soluble substances in liquids
what is the name given to the pencil line in paper chromatography
the baseline
Why should we use pencil for the baseline rather than pen? in paper chromatography
Pen ink would dissolve in the solvent and move up the paper
Should the baseline be submerged in the solvent?
no
What are some solvents commonly used in chromatography?
water and ethanol
What is the name of the resulting paper we end up with? in paper chromatography
a chromatogram
Which is the mobile phase in paper chromatography?
the solvent
what is meant by the mobile phase is chromatography
where the molecules can move - a liquid or a gas
what is the stationary phase in chromatography
where the molecules cant move - a soil or a thick liquid
what are the steps in the paper chromatography experiment
- take filter paper and use a pencil to draw line near bottom of paper - base line
- add ink to pencil line
- put shallow amount of solvent in beaker
- place filter paper in solvent - make sure pencil line is not submerged
- when solvent goes up paper in dyes in ink will dissolve and move up
what do the different chemical in the ink sample constantly change between in paper chromatography
the mobile and stationary phase
- dissolve in solvent, move a little bit, bind to paper
- this happens over and over again
what causes how far up the paper the different chemicals in the ink will travel
how long they spend in each phase
( mobile + stationary)
if the molecules are more soluble in the solvent which phase are they in more
they spend more time in the mobile phase and move up the paper faster
if the molecules are less soluble or more attracted to the paper what phase are they in more
they spend more time in the stationary phase and move up the paper slower
what is the Rf value
the distance travelled by the substance
divided by
the distance travelled by the solvent
Which is the stationary phase in paper chromatography?
the paper
what will happen if you change the mobile or stationary phase
you will get a different Rf value as the Rf value for a substance is specific to a particular mobile or stationary phase
