Chemical analysis

Question 1

What is the test for hydrogen?

Answer 1

lit splint in test tube filled with gas
squeaky pop is positive result

Question 2

What is the test for oxygen?

Answer 2

glowing splint in test tube filled with gas relights

Question 3

What is the chemical test for water?

Answer 3

anhydrous copper sulphate turns from white to blue

Question 4

What is the physical test for water?

Answer 4

measure boiling point
pure water boils at 100ºC
range of temps = impure

Question 5

What is the test for carbon dioxide?

Answer 5

bubble through limewater
turns cloudy

Question 6

What is the test for chlorine?

Answer 6

place damp blue litmus paper into gas
bleaches/turns white

Question 7

What is the test for ammonia?

Answer 7

place damp red litmus paper into gas
turns blue

Question 8

What is a positive ion?

Answer 8

cation

Question 9

What is a negative ion?

Answer 9

anion

Question 10

How do you conduct a flame test?

Answer 10

dip nichrome wire into HCl (cleans wire)
dip wire into sample
place wire into blue bunsen flame

Question 11

Why should the flame be non-luminous?

Answer 11

to see only one colour

Question 12

What colour does Li⁺ turn in flame test?

Answer 12

red

Question 13

What colour does Na⁺ turn in flame test?

Answer 13

yellow

Question 14

What colour does K⁺ turn in flame test?

Answer 14

lilac

Question 15

What colour does Ca²⁺ turn in flame test?

Answer 15

orange/red
(brick red)

Question 16

What colour does Cu²⁺ turn in flame test?

Answer 16

blue-green

Question 17

What is a precipitate?

Answer 17

solid formed from mixing two solution

Question 18

How do you conduct a sodium hydroxide test?

Answer 18

dissolve sample in distilled water
add a few drops of sample to test tube
add a few drops of NaOH to the sample

Question 19

What colour is the precipitate when using Cu²⁺ in sodium hydroxide test? and what is the precipitate formula?

Answer 19

blue
Cu(OH)₂

Question 20

What colour is the precipitate when using Fe²⁺ in sodium hydroxide test? and what is the precipitate formula?

Answer 20

green
Fe(OH)₂

Question 21

What colour is the precipitate when using Fe³⁺ in sodium hydroxide test? and what is the precipitate formula?

Answer 21

brown
Fe(OH)₃

Question 22

How do you test for ammonium ions?

Answer 22

dissolve sample in distilled water (if solid)
add NaOH and warm
Put damp red litmus paper into the gas produced

Question 23

How do you conduct a halide test?

Answer 23

dissolve sample in distilled water (if solid)
add nitric acid (HNO₃) → (prevents false positives)
add a few drops of silver nitrate solution (AgNO₃)
precipitate will form

Question 24

What colour is the precipitate when using Cl⁻ in halide test? and what is the precipitate formula?

Answer 24

white
AgCl → silver chloride

Question 25

What colour is the precipitate when using Br⁻ in halide test? and what is the precipitate formula?

Answer 25

cream AgBr → silver bromide

Question 26

What colour is the precipitate when using I⁻ in halide test? and what is the precipitate formula?

Answer 26

yellow AgI → silver iodide

Question 27

What is the ionic equation for this full equation: KCl + AgNO₃ → AgCl + KNO₃

Answer 27

Cl⁻ + Ag → AgCl

Question 28

How do you test for carbonate ions?

Answer 28

add HCl → look for effervescence yes = bubble gas through limewater, turns cloudy if carbonate no = not a carbonate

Question 29

How do you test for sulphate ions?

Answer 29

Add HCl → look for effervescence yes = check for carbonate no = add barium chloride solution, if sulphate , white precipitate formed