chemical analysis

Question 1

what is chemical analysis

Answer 1

the instruments and methods used to
seperate
identify
quantify
different substances

Question 2

what are examples of chemical analysis

Answer 2

chromotography
crystallisation
distillation
filtration

Question 3

define a pure substance

Answer 3

something that contains only 1 types of compound or element

Question 4

what are 2 examples of pure substances

Answer 4

distilled water
sodium chloride

Question 5

why is it important to know purity of substances

Answer 5

only pure subtances melt and boil at specific temps

Question 6

mp of nacl

Answer 6

801 degrees

Question 7

example of how can we use a physical test to identify substances

Answer 7

boil unknown liquid
it boils at 100 degrees
we can be quite sure it is water

Question 8

what is a chemical test

Answer 8

reacting a substance with another chemical to determine what it is is chemical

Question 9

what is a physical test

Answer 9

testing physical properties(eg mp or bp) and looking them up in big data book to find match

Question 10

state the mp and bp patterns for impure substances

Answer 10

they melt and boil over large range of temps

Question 11

what does having impurities in a sample generally do

Answer 11

lower mp
increase bp

Question 12

what is the mp/bp for salt water

Answer 12

mp=-2 degrees
bp=100.5 degrees

Question 13

what are formulations

Answer 13

mixtures prepared using specific formula

Question 14

How and why are formulations made

Answer 14

-so they have precise amounts of different components
-have a particular function

Question 15

what are 7 examples of formulations

Answer 15

fuels
cleaning agents
paint
medicines
alloys
fertilisers
food and drink

Question 16

describe the idea of formulations to a recipe and meal

Answer 16

a recipe that makes a mixture for a specific purpose

Question 17

what is the rule with formulations

Answer 17

the different components(that give diff properties) are in carefully measured quantities

Question 18

what is are the components needed in the formulation of green paint

Answer 18

green colour
stick to the wall
many others

Question 19

what is paper chromotography used for

Answer 19

to seperate different dyes in an ink
which are
mixtures of soluble substances in liquids

Question 20

what is the 1st step of paper chromotography

Answer 20

draw line near bottom of sheet of a4 filter paper called baseline using pencil.

Question 21

what is the 2nd step of paper chromatography

Answer 21

add sample of ink(that you think has many dyes) in centre of baseline

Question 22

what is the 3rd step of paper chromotography

Answer 22

put a shallow amount of solvent like ethanol or water into beaker

Question 23

what is the 4th step of paper chromotography

Answer 23

put filter paper into solvent but dont submerge the baseline

Question 24

what is the 5th step of paper chromotography

Answer 24

place lid so solvent does not evaporate

Question 25

results after step 5 of paper chromatography

Answer 25

solvent seeps up paper different dyes that make up ink dissolve in solvent and move up with it

Question 26

how does paper chromatograpy seperate different substances

Answer 26

each dye travels at different rates an d seperate out

Question 27

why may stay some chemicals stay on the baseline

Answer 27

as they arent soluble in solvent so they cant dissolve and move up paper

Question 28

what is the 6th step of paper chromotography

Answer 28

take filter paper out and leave it to dry when solvent has almost reached top of paper

Question 29

what is a chromatogram

Answer 29

the pattern of spots we have left on our filter paper

Question 30

what is the mobile phase

Answer 30

substance that molecules can move in typically liquid or gas

Question 31

what is the mobile phase in chromatography

Answer 31

solvent used

Question 32

what is the stationary phase

Answer 32

substance that molecules cant move in typically solid or very thick liquid

Question 33

what is the stationary phase in paper chromatography

Answer 33

paper

Question 34

what happens to the chemicals in the ink sample in terms of phases in paper chromatography

Answer 34

they constantly change between the mobile and stationary phases

Question 35

what is an example of changes in phases in paper chromatography

Answer 35

dissolving in solvent moving slightly binding to paper repeat

Question 36

what determines how fast chemicals in paper chromatography move up paper

Answer 36

how long they spend in each phase

Question 37

what is the relation between solubility and speed in paper chromatography

Answer 37

more soluble in spends more time in mobile phase so goes faster and travels further up paper less soluble spend more time in stationary phase so are slower and wont travel far up paper

Question 38

what makes less soluble chemicals slower

Answer 38

as they are more attracted to the paper

Question 39

how can we identify chemicals in paper chromatography

Answer 39

measure how far substance move and compare it to a data book

Question 40

what 2 factors affect how far chemicals move up paper

Answer 40

properties of substance how long we leave experiment

Question 41

what is the rf value

Answer 41

a ratio

Question 42

what is the equation for the rf value

Answer 42

distance travelled by substance/ distance travelled by solvent

Question 43

what happens to a pure substance in paper chromatography

Answer 43

doesnt seperate out at all -appears as a dot on the chromatogram

Question 44

what may change the rf value you get for a pure substance

Answer 44

using different solvent diff type of paper

Question 45

Why should we use pencil for the baseline rather than pen?

Answer 45

Pen ink would dissolve in the solvent and move up the paper tampering with experiment

Question 46

what is the rf value of a substance specific to

Answer 46

stationary phase(paper) solvent(mobile phase)

Question 47

1st step in chlorine test

Answer 47

get test tube full of sample gas(which u think may be chlorine)

Question 48

2nd step in chlorine test

Answer 48

dampen blue litmus paper

Question 49

3rd step in chlorine test

Answer 49

put litmus paper into test tube

Question 50

what happens if chlorine is present in step 3 of cl test

Answer 50

litmus paper goes blue----->white

Question 51

why may chlorine briefly go red before turning white in cl test

Answer 51

it dissolves in water forming hcl which is acidic and turns blue litmus red

Question 52

why does litmus go back to white after turning red

Answer 52

it gets bleached by the chlorine

Question 53

what /why precautions are taken in cl test

Answer 53

cl is poisonous so wear mask or perform it in a fume cupboard

Question 54

what is needed in o2 test

Answer 54

a glowing splint sample of gas

Question 55

explain steps of o2 test

Answer 55

place splint into tube and if it relights its oxygen

Question 56

why does the splint relight in o2 test

Answer 56

burning requires o2

Question 57

equipment needed for h2 test

Answer 57

burning splint test tube sample

Question 58

what happens if h2 is present in h2 test

Answer 58

squeaky pop heard as splint is brought near

Question 59

why is squeaky pop heard in h2 test

Answer 59

heat energy from flame causes hydrogen to burn with o2 in air to form water

Question 60

what is equipment for co2 test

Answer 60

test tube of gas sample test tube of colourless limewater( aq calcium hydroxide)

Question 61

steps for co2 test

Answer 61

bubble sample gas into limewater test tube solution goes cloudy if it is co2

Question 62

why does solution go cloudy in co2 test

Answer 62

co2(g) and ca(oh)2(g) react to form caco3(s) and h20(l) caco3 is solid and its small solid particles make it appear cloudy