Chemical analysis and electolysis

Question 1

What are flame tests used for?

Answer 1

Identifying metal ions

Question 2

Lithium flame

Answer 2

crimson

Question 3

Sodium flame

Answer 3

Yellow

Question 4

Potassium flame

Answer 4

Lilac

Question 5

Calcium flame

Answer 5

Red

Question 6

Barium flame

Answer 6

Green

Question 7

How do you flame test a compound?

Answer 7

dip a clean wire loop into a sample of the compound and put the wire loop in the clear blue part of bunsen flame
Make sure the loop is clean by dipping it into HCl and rinsing with distilled water

Question 8

Chlorine gas test

Answer 8

bleaches damp litmus paper, turning it white (may turn red because chlorine solution is acidic)

Question 9

Test for oxygen

Answer 9

relighting a glowing splint

Question 10

Test for hydrogen

Answer 10

squeaky pop with lighted splint (comes from hydrogen burning with the oxygen in the air to form H2O)

Question 11

What do you do if the flame test for metals doesn’t work?

Answer 11

some metals form a coloured precipitate with NaOH

Question 12

Calcium hydroxide

Answer 12

white

Question 13

copper hydroxide

Answer 13

blue

Question 14

Fe(OH)2

Answer 14

green

Question 15

Fe(OH)3

Answer 15

brown

Question 16

aluminium hydroxide

Answer 16

white at first. then dissolves and goes colourless

Question 17

Magnesium hydroxide

Answer 17

White

Question 18

CO2 test

Answer 18

bubble through limewater turns cloudy,

test for carbonates

Question 19

Halide test

Answer 19

different precipitates formed,
add dilute nitric acid and the silver nitrate solution
chloride white
bromide cream
iodide yellow

Question 20

Sulfate test

Answer 20

dilute HCl and dilute barium chloride solution

white precipitate

Question 21

Mobile phase

Answer 21

where molecules can move, liquid or gas

Question 22

stationary phase

Answer 22

where molecules can’t move, solid or thick liquid

Question 23

How does chromatography work?

Answer 23

dynamic equilibrium between mobile and stationary phase, chemical separate out and travel at different speeds

Question 24

Paper chromatography

Answer 24

chemicals dissolve in solvet (ethanol or water) and move in dynamic equilibrium between paper and solvent
the chemicals that spend more time in the mobile phase form spots further up the paper

Question 25

What does the amount of time spent in each phase depend on in paper chromatography?

Answer 25

how soluble molecules are

how attracted they are to the paper

Question 26

stationary phase in TLC

Answer 26

silica gel spread onto a glass plate

Question 27

What is the result of chromatography analysis called?

Answer 27

chromatogram

Question 28

What happens if chromatography spots are colourless?

Answer 28

locating agent

Question 29

What is an Rf value?

Answer 29

ratio between distance travelled by solute and distance travelled by solvent

Question 30

Rf formula

Answer 30

distance travelled by solute/distance travelled by solvent

Question 31

Phenophthalein

Answer 31

pink alkali

colourless in acids

Question 32

Methyl orange

Answer 32

yellow alkali

red acids

Question 33

Electrolysis of lead bromide

Answer 33

molten

negative electrode accepts two electrons to become one lead atom etc

Question 34

Electroplating

Answer 34

uses electrolysis to coat the surface of one metal with another metal
metal ions travel to cathode and electrode gains mass