C8 Chemical analysis

Question 1

What is a pure substance?

Answer 1

a substance with only 1 element/compound throughout

Question 2

How can we test how pure a substance is?

Answer 2

we can compare MP/BP and the closer to the actual value, the purer it it.

Question 3

What is the effect of impurities on the melting point?

Answer 3

impurities lower the melting point

Question 4

What is the effect of impurities on the boiling point?

Answer 4

impurities increase the boiling point of a sample

Question 5

what are formulations?

Answer 5

useful mixtures made of exact amounts of components

Question 6

What is in the formulation of paint?

Answer 6

pigment
solvent
binder
additives

Question 7

Why are formulations useful in the pharmacutical industry?

Answer 7

so chemists can ensure drugs are delivered to the correct part of the body, at the right concentration and has a long shelf life

Question 8

What is chromatography?

Answer 8

a method to seperate the substances of a mixture

Question 9

what are the 2 phases in chromatography?

Answer 9

a mobile phase

a stationary phase

Question 10

how do you calculate the Rf value from chromatography?

Answer 10

distance travelled by solvent

Question 11

What has to be done to make chromatography useful?

Answer 11

test a pure substance next to it so you can compare

Question 12

What is the test for chlorine?

Answer 12

bleeches damp litmus paper white

Question 13

What is the test for oxygen?

Answer 13

ignites a glowing splint

Question 14

What is the test for carbon dioxide?

Answer 14

turns lime water (calcium hydroxide) cloudy

Question 15

What si the test for hydrogen?

Answer 15

makes a squeaky pop when ignited with a lit splint

Question 16

What are the 3 test for anions?

Answer 16

dilute acid-to test for carbonates
barium chloride and HCL- can test for sulphates
nitric acid and silver nitrate can test for halides

Question 17

How can you test for carbonates?

Answer 17

add dilute acid and see if it turns limewater cloudy as co2 is released

Question 18

How can you test for sulfates?

Answer 18

add a few drops on HCL and a few drops of barium chloride. a white precipitate will form if sulfate ions are present

Question 19

How can you test for halides

Answer 19

add a few drops of nitric acid and silver nitrate.

the colour of precipitate determines the halide ion

Question 20

In a halide ion test, what precipitates do chloride ions form?

Answer 20

white

Question 21

In a halide ion test, what precipitates do bromide ions form?

Answer 21

cream

Question 22

In a halide ion test, what precipitates do iodide ions form?

Answer 22

yellow

Question 23

What colour flame to lithium ions burn with?

Answer 23

crimson

Question 24

What colour flame to sodium ions burn with?

Answer 24

yellow

Question 25

What colour flame to potassium ions burn with?

Answer 25

lilac

Question 26

What colour flame to calcium ions burn with?

Answer 26

orange-red

Question 27

What colour flame to copper ions burn with?

Answer 27

green

Question 28

Why do you clean the loop in HCL in flame tests?

Answer 28

to ensure the loop isnt contaminated

Question 29

What is a disadvantage of flame tests?

Answer 29

you can only detect samples that contain a single metal ion and not a mixture

Question 30

what 2 ways can you test for cations?

Answer 30

flame tests | adding NaOH

Question 31

What colour precipitate does calcium form when NaOH is added?

Answer 31

white

Question 32

What colour precipitate does copper form when NaOH is added?

Answer 32

blue

Question 33

What colour precipitate does iron(II) form when NaOH is added?

Answer 33

green

Question 34

What colour precipitate does iron (III) form when NaOH is added?

Answer 34

brown

Question 35

What colour precipitate does magnesium form when NaOH is added?

Answer 35

white

Question 36

What colour precipitate does aluminium form when NaOH is added?

Answer 36

White at first but then redissolves in excess NaOH to form a colourless soloution

Question 37

What is flame emission spectroscopy?

Answer 37

when a sample is placed in a flame. as the ions heat up, their electrons become excited. when they then drop down to their original energy level, they transfer energy as light which can pass through a stechoscope ad detect different wavelengths of light

Question 38

What does the combination of a wavelength emitted by an ion?

Answer 38

is charge and electron arrangement.

Question 39

What can flame emission spectroscopy be used for?

Answer 39

identifying ions in solutions and calculating concentrations

Question 40

Why are machines used for analysing unknown substances (instrumental analysis)?

Answer 40

very sensitive very fast very accurate

Question 41

Does flame emission spectroscopy work for mixtures?

Answer 41

yes- this is why its more useful than flame tests