CHEMICAL ANALYSIS

Question 1

what is a pure substance

Answer 1

contains only one type of compound or element

Question 1

how to test substances off boiling points

Answer 1

boil them - see boiling point - look up what chemical has that

Question 2

define formulation

Answer 2

mixtures that have been prepared using a specific formula (precise amounts of diff compounds)
(have a particular function)

Question 3

examples of formulations

Answer 3

fuels
cleaning agents
paint
medicines
alloys
fertilisers

Question 4

True or false? Pure substances always melt and boil at specific temperatures.

Answer 4

true

Question 5

If we test a substance for purity by measuring its boiling point, is that a physical test or a chemical test?

Answer 5

physical

Question 6

what is chromatography used for

Answer 6

separate substances in a mixture

Question 7

method for paper chromatography (req prac)

Answer 7

1. draw baseline w pencil
2. add sample in spots on baseline
   3.place paper in solvent so baseline is above level
3. remove and measure distances traveled by solvent and each spot
4. calculate Rf values

Question 8

how to calculate Rf values

Answer 8

distance moved by substance / distance moved by solvent

Question 9

what si the mobile phase

Answer 9

the substance that the molecules can move in e.g liquid gas solvent

Question 10

what is the stationary phase

Answer 10

substance the molecules cannot move in e.g chromatography paper

Question 11

What are some solvents commonly used in chromatography?

Answer 11

ethanol
water

Question 12

test for chlorine

Answer 12

bleaches damp litmus paper

Question 13

test for oxygen

Answer 13

relights glowing splint
put glowing splint into test tube

Question 14

test for hydrogen

Answer 14

squeaky pop
put burning splint into test tube

Question 15

test for carbon dioxide

Answer 15

bubble through limewater
turns limewater cloudy

Question 16

what are anions

Answer 16

negatively charged ions

Question 17

what is formed when a carbonate reacts w an acid

Answer 17

salt
carbon dioxide
water

Question 18

test for carbonates

Answer 18

add dilute HCl
take any gas produced + run through limewater
positive result = goes cloudy bc CO2 present

Question 19

test for sulphates

Answer 19

add dilute HCl (remove any other ions)
add barium chloride solution
positive result = white precipitate form

Question 20

test for halide ions (chloride bromide iodide)

Answer 20

add dilute nitric acid
add silver nitrate
positive result for
chloride = white ppt.
bromide = cream ppt.
iodide = yellow ppt.

Question 21

what is a cation

Answer 21

ions with a positive charge

Question 22

method to testing for cations

Answer 22

1. clean nichrome wire loop, clean it , rinse it , heat it
2. dip loop in compound being tested
3. hold wire loop in flame
4. see what colour

Question 23

In preparation for the flame test, which two of the following are used to clean the platinum wire loop?

Answer 23

HCl
bunsen flame

Question 24

what colour does lithium ions burn w

Answer 24

crimson

Question 25

what colour do sodium ions burn w

Answer 25

yellow flame

Question 26

what colour do potassium ions burn w

Answer 26

lilac flame

Question 27

what colour do calcium ions burn w

Answer 27

orange/red flame

Question 28

what colour do copper ions burn w

Answer 28

green flame

Question 29

acronym for flame tests

Answer 29

LITTLE CHILDREN SHOULD YODEL POSITIVELY LIKE COWS RUNNING CROSS GRASS LITHIUM CRIMSON SODIUM YELLOW POTASSIUM LILAC CALCIUM RED COPPER GREEN

Question 30

metal hydroxide test ( calcium iron iron magnesium aluminium copper)

Answer 30

add dilute sodium hydroxide Ca 2+ = WHITE PPT. Fe 2+ = GREEN PPT. Fe 3+ = BROWN PPT. Mg 2+ = WHITE PPT. Al 3+ = WHITE AT FIRST BUT IN EXCESS REDISSOLVES TO FORM COLOURLESS Cu 2+ = BLUE PPT.

Question 31

main piece of equipment used in flame emmision spec

Answer 31

spectroscope ( detects the individual wavelngths that are emitted)

Question 32

pros of flame emission spec

Answer 32

can see multiple diff metal ions - can identify unknown metal ions in sample concentration of ion (intensity of line)

Question 33

3 main benefits of spectroscopy

Answer 33

v accurate v sensitive v fast

Question 34

con of spectroscopy

Answer 34

uses expensive materials

Question 35

When metal ions are heated they start to ________ light.

Answer 35

emit

Question 36

If a substance contains multiple ---------, all of their line spectrums will be combined into a single line spectrum.

Answer 36

anions