2.h - Chemical tests

Question 1

test for ammonia gas

Answer 1

1. add sodium hydroxide and gently warm = if ammonia present = stinky smell
2. damp ( so ammonia gas can dissolve ) piece of red litmus paper = if ammonia present= paper turns blue

Question 2

test for carbon dioxide

Answer 2

limewater

if CO2 present = turns limewater cloudy

Question 3

what are methods of collection for carbon dioxide ( 2 method)

Answer 3

collected over water ( CO2 slightly soluble in water + denser than air ) = gas jar on beehive shelf in a trough of water ( pushes less dense air out of the top of the jar )

Question 4

what is a cheap of producing carbon dioxide

Answer 4

calcium carbonate + hydrochloric acid = carbon dioxide + calcium chloride + water

Question 5

(1st way) of collecting carbon dioxide

Answer 5

thermal decomposition copper carbonate (green powder)

copper carbonate = carbon dioxide + copper oxide

heat copper (II) carbonate and collect the gas ( CO2) given off in a test tube.

Question 6

what do flame test identify

Answer 6

metal ions

Question 7

how do you carry out a flame test

Answer 7

1. clean platinum wire loop by dipping it into some dilute HCl (hydrochloric acid )
2. then hold it in a flame
3. once loop burns in flame without any colour dip it into sample you want to test
4. the put loop ( with sample testing on it ) back in the clear blue part of the Bunsen burner flame

Question 8

flame test - red flame =?

Answer 8

Lithium = Li+

Question 9

flame test - yellow- orange flame =?

Answer 9

Sodium = Na+

Question 10

flame test - lilac flame =?

Answer 10

Potassium = K+

Question 11

flame test - brick red flame =?

Answer 11

Calcium = Ca 2+

Question 12

flame test - blue-green flame =?

Answer 12

Copper= Cu 2+

Question 13

what colour flame does Lithium, Li+ produce

Answer 13

red

Question 14

what colour flame does Sodium, Na+ produce

Answer 14

yellow-orange

Question 15

what colour flame does Potassium, K+ produce

Answer 15

lilac

Question 16

what colour flame does Calcium, Ca 2+ produce

Answer 16

brick red

Question 17

what colour flame does Copper, Cu 2+ produce

Answer 17

blue-green

Question 18

what is the test for the halide ions (Cl-, Br-, I- )

Answer 18

acidified (nitric acid) sliver nitrate ( produces silver (ides) precipitates )

acid added yo get rid of carbonate or sulphite ions before the test

Question 19

what does a chloride ion + silver nitrate =?

Answer 19

White precipitate of silver chloride

Question 20

what does a bromide ion + silver nitrate =?

Answer 20

Cream precipitate of silver bromide

Question 21

what does a iodide ion + silver nitrate =?

Answer 21

Yellow precipitate of silver iodide

Question 22

what is the test for hydrogen

Answer 22

makes a squeaky pop with a lighted splint ( noise comes from hydrogen burning with the oxygen in the air to form H20

Question 23

what is the test for oxygen

Answer 23

relights a glowing splint

Question 24

what is the test for chlorine

Answer 24

bleaches damp blue litmus paper turning it white ( may turn red for a moment though because solution of chlorine is acidic )

Question 25

what is the test for NH4+ ions ( ammonium ions )

Answer 25

adding dilute sodium hydroxide solution + gently heating = ammonia gas ( pungent smell + turns damp red litmus paper blue )

Question 26

test for copper ( II ) + sodium hydroxide = ???

Answer 26

blue precipitate of copper ( II ) hydroxide

Question 27

test for iron ( II ) + sodium hydroxide = ???

Answer 27

sludgy green precipitate of iron ( II ) hydroxide

Question 28

test for iron ( III ) + sodium hydroxide = ???

Answer 28

reddish brown precipitate of iron ( III ) hydroxide

Question 29

test for sulphate ions ( SO4 2-)

Answer 29

add acidified barium chloride ( add HCl + barium chloride solution) = white precipitate of barium sulphate ( needs to be acidified to get rid of any traces of carbonate or sulphate ions cos both would produce a precipitate )

Question 30

test for carbonates ( CO3 2- )

Answer 30

add dilute hydrochloric acid = carbon dioxide gas ( test using limewater)

Question 31

test for the presence of water

Answer 31

add few drops of solution to anhydrous copper ( II ) sulphate water present = white powder turn blue

Question 32

describe physical test to show whether a sample of water is pure

Answer 32

pure = only made of 1 substance = has set defined physical properties eg. boiling + freezing point pure water will always = boil at 100*c + freeze at 0*c