Chemical analysis

Question 1

what is everyday purity?

Answer 1

-nothing added to it e.g beeswax

Question 2

what is chemical purity?

Answer 2

-only contains one element or compound

Question 3

how to test purity of sample?

Answer 3

• have specific m/bpts
• compare with m/bpts in data book

closer measured value to actual, purer the sample

Question 4

what do impurities do to samples?

Answer 4

-lower mpt and increase range

increase bpt and increase range

Question 5

what are formulations?

Answer 5

• useful mixture with precise purpose made by formula
• measured quantities of components contributes to properties so it meets function

Question 6

paints are formulations composed of:

Answer 6

• pigment: colour e.g titanium oxide in white paints
• solvent: dissolve components and alter viscosity
• binder: forms film holds pigment in place after painted on
• additives: further change physical and chemical properties

Question 7

how are formulation important in pharmaceutical industry

Answer 7

• alter formulation of pill so delivers to right body part
• right conc
• consumbale
• long shelf life

Question 8

info on composition is found on labels

Answer 8

• ratio or percentage of each component
• choose formulation with right composistion of particular use

Question 9

what is a mobile phase?

Answer 9

-molecules can move in liquid or gas

Question 10

what is a stationary phase?

Answer 10

molecules can’t move in solid or real thick liquid

Question 11

what effects how quick chemical moves or how spots are formed?

Answer 11

• distribution: more time in m than s moves further up paper
• spots form if chemicals spend diff time in m
• no. of spots depend on solvent
• pure substance forms one spot in any solvent

Question 12

amount of time molecules spend in each phase depends on?

Answer 12

• solubility of solvent
• how attracted to paper
• higher solubility and less attraction means longer in m

Question 13

what is the Rf value and its calculation?

Answer 13

• ratio between distance travelled by solute and solvent
• distance by solute/distance by solvent

Question 14

how to test for chlorine?

Answer 14

• bleaches damp litmus paper white
• red for a sec cuz acidic

Question 15

how to test for oxygen?

Answer 15

glowing splint inside test tube and will relight

Question 16

how to test for CO₂

Answer 16

bubble it thru aquaeous solution of limewater, turns cloudy

Question 17

how to test for hydrogen?

Answer 17

hold lit splint at end of test tueb and get squeaky pop

Question 18

how to test for carbonates?

Answer 18

• add drops of dilute HCl with pipette
• connect to test tube of limewater
• if ions present then limewater cloudy

Question 19

how to test for sulfates?

Answer 19

• add drops of HCl then barium chloride solution to test tube
• if ions present white barium sulfate precipitate form

Question 20

how to test for halides?

Answer 20

• add drops of dilute nitric acid then drops of silver nitrate solution
• white precipitate silver chloride
• cream precipitate of silver bromide
• iodide precipitate of silver iodide

Question 21

compounds of some metals burn with…

Answer 21

characteristic flame

Question 22

Lithium burns with

Answer 22

crimson flame

Question 23

sodium burns with

Answer 23

yellow flame

Question 24

potassium burns with

Answer 24

lilac flame

Question 25

calcium burns with

Answer 25

orange-red flame

Question 26

copper burns with

Answer 26

green flame

Question 27

how to carry out a flame test?

Answer 27

1. clean platinum wire loop in dilute HCl
2. hold in blue flame from bunsen until burns colourless
3. dip loop into sample and into flame and record colour
   4.

Question 28

what a flame tests used for?

Answer 28

• identify different metal ions
• only works for sample with single cation
• if contains mixture, flame colours of some ions hidden by others

Question 29

how to test for cations in compounds?

Answer 29

• many metal hydroxides insoluble and precipitate out of solution
• add drops of sodium hydroxide to get coloured insoluble hydroxide

Question 30

calcium and OH gives what precipitate?

Answer 30

white

Question 31

copper and OH gives what precipitate?

Answer 31

blue

Question 32

iron (II) and calcium gives what precipitate?

Answer 32

green

Question 33

iron (III) and calcium gives what precipitate?

Answer 33

brown

Question 34

aluminium and calcium gives what precipitate?

Answer 34

white at first but redissolves in excess NaOH to form colourless solution

Question 35

magnesium and calcium gives what precipitate?

Answer 35

white

Question 36

how to carry out flame emission spectroscopy?

Answer 36

1. place sample in flame to heat ions and energise electrons
2. dropped energy levels transfer energy as light
3. passes thru spectroscope to detect diff wavelengths of light to make line spectrum

Question 37

what does combination of wavelengths emmited by an ion depend on?

Answer 37

• charge and electron arrangement
• diff ions emit diff wavelengths of light
• so has diff pattern and line spectrum

Question 38

what does intensity of spectrum indicate?

Answer 38

-conc of that ion in solution

Question 39

what are line spectrums used for?

Answer 39

• identify ions in solution
• calculate their concentration

Question 40

what are advantages of using machines compared to conducting test?

Answer 40

• very sensitive
• very fast
• very accurate