Chemical Analysis Year 11

Question 1

define purity and give an example of a pure substance

Answer 1

a single element/compound that is NOT mixed with any other substance
ie diamond

Question 2

give the formula for RF value

Answer 2

distance COMPONENT traveled/distance SOLVENT traveled

Question 3

what should RF value be given to (sf)

Answer 3

2sf

Question 4

what numbers should RF value be between

Answer 4

0 and 1

Question 5

what does the distribution of the components in the sample depend on

Answer 5

relative attraction to the paper and solvent

Question 6

define a formulation

Answer 6

PURE substances carefully mixed in specific proportions to have desired propertied

Question 7

what can RF values be used for

Answer 7

to identify substances in a solvent

Question 8

comment on RF values from substance to substance

Answer 8

different compounds have different RF values

Question 9

what is the gas test for hydrogen

Answer 9

lighted splint emits a squeaky pop

Question 10

what is the gas test for oxygen

Answer 10

glowing spilt will relight

Question 11

what is the gas test for CO2

Answer 11

turns limewater from clear to cloudy

Question 12

what is the gas test for chlorine

Answer 12

turns BLUE litmus paper RED the bleaches it

Question 13

describe the importance of gas tests

Answer 13

must identify substances present for:

• safety
• helps to identify substances present

Question 14

what is the trend of melting/ boiling points for pure substances

Answer 14

the all have very specific temperatures

Question 15

give substances where purity is especially importants

Answer 15

• medication
• baby food
• cosmetics

Question 16

give a possible suggestion of a melting point of a pure substance

Answer 16

88-89*C

Question 17

give examples of formulations

Answer 17

• alloys
• fertilisers
• gold jewellery

Question 18

state the speed at which substances with a stronger attraction to the paper will travel

Answer 18

slower and move less far up the paper

Question 19

state the speed at which substances with a weaker attraction to the paper will travel

Answer 19

faster and move further up the paper

Question 20

what is RF value

Answer 20

ratio of distance moved by substances to solvents

Question 21

how could RF values be different if different solvents/stationary phases are used

Answer 21

the substances could have a stronger/ weaker attraction to the stationary phase so they would move quicker/slower therefore RF value is altered

Question 22

how could RF values be different if different solvents are used

Answer 22

solvents could be less soluble so wouldn’t dissolve all of the compounds

Question 23

what are the two phases called in chromotography

Answer 23

-

Question 24

in paper chromatography, how many spots will a pure substance form on the paper

Answer 24

-

Question 25

give the formula for working out the Rf value of a substance

Answer 25

-

Question 26

how can you test if a gas in a test tube is oxygen?

Answer 26

-

Question 27

describe how paper chromotography works to separate mixtures

Answer 27

-

Question 28

what colour does litmus paper turn in the presence of chlorine

Answer 28

• white (if it goes red for a moment its bc chlorine is acidic)

Question 29

would you expect the Rf value of a substance to change if you changed the solvent in the chromatography experiment. why?

Answer 29

-

Question 30

a student collects gas given off during a reaction & bubbles go through limewater. the limewater goes cloudy. identify the gas produced

Answer 30

• carbon dioxide