c12- chemical analysis

Question 1

what is chromatography?

Answer 1

a technique that separates mixtures of substances with different levels of solubility

Question 2

molecule

Answer 2

two or more atoms chemically joined

Question 3

compound

Answer 3

two or more different atoms that are chemically joined

Question 4

solvent

Answer 4

the substance that the solute is dissolved in

Question 5

solute

Answer 5

what is dissolved in the solvent

Question 6

solution

Answer 6

mixture of solvent and solute

Question 7

mobile phase

Answer 7

​gas or liquid that carries the component - moves with the sample

Question 8

stationary phase

Answer 8

the part of the apparatus that does not move with the sample

Question 9

why do you draw the baseline in pencil?

Answer 9

the ink would interfere with the solvent

Question 10

retention factor (Rf) values

Answer 10

• Rf factor used to compare the components of various samples
• the unknown Rf values can be compared with the known value
• if two substances have the same Rf value then it is likely that they are of the same compound

Question 11

Rf equation

Answer 11

distance from the baseline to the spot / distance from the baseline to the solvent front

Question 12

test for hydrogen

Answer 12

a lit wooden splint makes a popping sound in a test tube of hydrogen.

Question 13

test for oxygen

Answer 13

a glowing wooden splint relights in a test tube of oxygen.

Question 14

test for carbon dioxide

Answer 14

carbon dioxide turns limewater cloudy/milky

Question 15

test(s) for chlorine

Answer 15

• sharp smell
• bleaches damp blue litmus paper
• makes damp starch-iodide paper turn blue-black

Question 16

what is a pure substance?

Answer 16

a substance made up of only one time of atom or molecule OR single element or compound that is not mixed with any other substance

Question 17

what is the physical test for water?

Answer 17

• melting point: 0 degrees
• boiling point: 100 degrees

Question 18

how can you test if a substance is pure?

Answer 18

you can use their melting and boiling points

Question 19

what happens if the substance is impure in terms of melting and boiling points?

Answer 19

• when something is impure, it boils over a range, rather than a single degree
• the MORE impure something is, the LOWER the melting point (+ a larger range)
• the MORE impure something is, the HIGHER the boiling point

Question 20

what is a formulation?

Answer 20

• useful mixture with a precise purpose (!!!)
• they are made by following a specific ‘formula’
• each component in a formulation is present in a measured quantity, and contributes to the properties of the formulation so it meets its required function

Question 21

what makes paint a formulation?

Answer 21

• pigment: gives the paint colour
• solvent: used to dissolve other components and alter the viscosity
• binder: forms a film that holds the pigment in place after it has been painted onto a surface
• additives: added to further change the physical and chemical properties of the paint

Question 22

examples of pure substances:

Answer 22

• distilled water
• bar or iron
• acetone
• hexane

Question 23

examples of formulations:

Answer 23

• face cream
• paint
• nail varnish
• alloys
• drugs/medicines
• cleaning agents

Question 24

what is the test for hydrogen?

Answer 24

a lit wooden splint makes a popping sound in a test tube of hydrogen

Question 25

what is the test for oxygen?

Answer 25

a glowing wooden splint relights in a test tube of oxygen

Question 26

what is the test for carbon dioxide?

Answer 26

carbon dioxide turns limewater cloudy/milky

Question 27

what is the test for chlorine?

Answer 27

sharp smell, bleaches damp blue litmus paper, makes damp starch-iodide paper turn blue/black

Question 28

what is the test for carbonates? and what is the observations?

Answer 28

- you add a dilute acid to a carbonate - it fizzes (effervescence) and produces carbon dioxide gas (lime water becomes cloudy)

Question 29

what is the test for chloride ions?

Answer 29

- add dilute nitric acid and then a silver nitrate solution - a white precipitate forms

Question 30

what is the test for bromide?

Answer 30

- add dilute nitric acid and then a silver nitrate solution - a cream precipitate forms

Question 31

what is the test for iodide?

Answer 31

- add dilute nitric acid and then a silver nitrate solution - a yellow precipitate forms

Question 32

what is the test for sulfates?

Answer 32

- adding a dilute hydrochloric acid followed by a barium chloride solution - a white precipitate tells you that sulfate ions are present

Question 33

what is precipitate?

Answer 33

a solid formed by a change in a solution

Question 34

what is the test for halides on general?

Answer 34

1) add dilute nitric acid * removes any soluble carbonate or hydroxide impurities… because if those were present, then they’d alter the results 2) add a few drops of silver nitrate and a precipitate will form

Question 35

what is the test for sulfate ions?

Answer 35

1) acidify the sample with dilute hydrochloric acid and then add a few drops of aqueous barium chloride 2) if a sulfate is present and then a white precipitate of barium sulfate is formed

Question 36

what is a flame test?

Answer 36

1. wire loop is dipped in concentrated acid and heated why do have to heat it? * to get rid of contaminants like ions that are already on the loop 2) dip it into the compound to test and then place it into a bunsen burner flame

Question 37

how do you conduct a flame test?

Answer 37

1. wire loop is dipped in concentrated acid and heated why do have to heat it? * to get rid of contaminants like ions that are already on the loop 2) dip it into the compound to test and then place it into a bunsen burner flame

Question 38

what are the observations for the flame tests?

Answer 38

- lithium - crimson - sodium - yellow - potassium - lilac - calcium - orange/red - copper - green

Question 39

what is the test for the presence of Ca 2+? and what is the observation?

Answer 39

- add sodium hydroxide - forms a white precipitate - add more sodium hydroxide - no change; white precipitate remains

Question 40

what is the test for the presence of Mg 2+? and what is the observation?

Answer 40

- add sodium hydroxide - forms a white precipitate - add more sodium hydroxide - no change; white precipitate remains

Question 41

what is the test for the presence of Cu2+ and what is the observation?

Answer 41

- add sodium hydroxide - forms a blue precipitate

Question 42

what is the test for the presence of Fe2+ and what is the observation?

Answer 42

- add sodium hydroxide - forms a green precipitate

Question 43

what is the test for the presence of Fe3+ and what is the observation?

Answer 43

- add sodium hydroxide - forms a brown precipitate

Question 44

how do you diffrentiate between the presence of calcium and magnesium?

Answer 44

- by doing a further flame - if the flame turn orange-red if calcium present and if not, then magnesium is present

Question 45

what is the test for the presence of Al 3+and what is the observation?

Answer 45

- white precipitate - add more - white precipitate dissolves