chemical analysis

Question 1

what is the chemical test for hydrogen?

Answer 1

-collect a sample of gas in a test tube
-attempt to ignite the gas using a lit split
-squeaky pop sound

Question 2

what chemical reaction is taking place during the hydrogen test?

Answer 2

the combustion of H2 to form H20

Question 3

what is the pop sound caused by/

Answer 3

the hot gas rushing out of the test tube

Question 4

what is the test for oxygen?

Answer 4

-collect a sample of gas in a test tube
-place a glowing splint into the tube
-the splint relights

Question 5

what is the reaction taking place when testing for oxygen?

Answer 5

the combustion of the wood in the splint

Question 6

why does the glowing splint relight?

Answer 6

pure 02 is more concentrated than the 02 in normal air- the wood in the splint combusts faster

Question 7

what is the chemical test for the presence of H20?

Answer 7

-add water to anhydrous copper sulfate
changes from anhydrous white to hydrated blue

Question 8

what is the test for the purity of H20?

Answer 8

measure its boiling point and compare it to 100 degrees celsius-if it is closer to 100 degrees celsius, it is more pure

Question 9

what is the chemical test for carbon dioxide?

Answer 9

-bubble a sample of gas through limewater-turns cloudy

Question 10

what is limewater?

Answer 10

saturated calcium hydroxide solution

Question 11

what is the test for chlorine?

Answer 11

-place damp blue litmus paper in a sample of gas- it turns white (bleaches it)

Question 12

what does the chlorine do in the experiment?

Answer 12

dissolves into the dampness (H20) and removes the colour from blue litmus

Question 13

what is the test for ammonia?

Answer 13

-place damp red litmus paper in a sample of gas
-it turns blue

Question 14

why does the ammonia conduct this reaction?

Answer 14

-the NH3 reacts with the dampness (H20) to form 0H- ions
-the NH3 acts as a base by accepting H+ ions from the H20
-the OH- ions are whats left after H20 has lost H+ and they are alkaline so the red litmus paper turns blue

Question 15

are cations positive or negative?

Answer 15

positive

Question 16

many metal cations cause what to change colour?

Answer 16

a non-luminous (blue) bunsen flame

Question 17

how to conduct a flame test?

Answer 17

-dip a piece of nichrome into hydrochloric acid
-dip the wire into a sample of solid or solution
-place the tip of the wire into a non-luminous bunsen flame

Question 18

lithium turns a blue flame what colour?

Answer 18

red

Question 19

sodium turns a blue flame what colour?

Answer 19

yellow

Question 20

potassium turns a blue flame what colour?

Answer 20

lilac

Question 21

what colour does calcium turn a blue flame?

Answer 21

orange-red

Question 22

what colour does copper turn a blue flame?

Answer 22

blue-green

Question 23

what do you use sodium hydroxide to test for?

Answer 23

copper, iron (II) and iron (III)

Question 24

what do we use to test for copper, iron 2+ and iron 3+

Answer 24

sodium hydroxide

Question 25

if copper, iron (II) or iron (III) is present, what will form?

Answer 25

a metal hydroxide precipitate

Question 26

how to conduct the NaOH test?

Answer 26

-dissolve the sample in water -add a few drops of NaOH

Question 27

if the precipitate for NaOH turns blue, what metal cation is it?

Answer 27

Cu2+

Question 28

if the precipitate for NaOH turns green, what metal cation is it?

Answer 28

Fe2+

Question 29

if the precipitate for NaOH turns brown, what metal cation is it?

Answer 29

Fe3+

Question 30

how do we test for ammonium?

Answer 30

using sodium hydroxide

Question 31

how to conduct an ammonium test?

Answer 31

-dissolve the sample in water -add some NaOH and warm it test the gas with red litmus paper (the ammonium test)

Question 32

if NH4+ ions are present in the original sample, what colour will the litmus paper turn?

Answer 32

blue

Question 33

what do we use to test for halides?

Answer 33

the silver nitrate test

Question 34

what are the halide ions?

Answer 34

Cl-, Br- and I-

Question 35

how to conduct the halides test?

Answer 35

-dissolve the sample in water -add nitric acid (HNO3) -add silver nitrate solution (AgNO3)

Question 36

what happens in the halides test if Cl-, Br- or I- ions are present?

Answer 36

a precipitate forms with the Ag+ ions from the AgNO3

Question 37

if a white precipitate is formed in the halides test what halide ion was it?

Answer 37

Cl-

Question 38

if a cream precipitate is formed in the halides test what halide ion was it?

Answer 38

Br-

Question 39

if a yellow precipitate forms in the halides test, what halide was it?

Answer 39

I-

Question 40

what is the test for carbonates?

Answer 40

the gas turns the limewater cloudy

Question 41

how do you conduct an experiment to test for carbonates?

Answer 41

-add hydrochloric acid and look for effervescence -if effervescence is present, bubble the gas through limewater -if CO32- were present, the gas evolved turns the limewater cloudy

Question 42

what is the test for sulfates?

Answer 42

white precipitate will form

Question 43

how do you conduct an experiment for sulfates?

Answer 43

-add hydrochloric acid and look for effervescence -if there is no effervescence, add barium chloride solution -if SO42- ions are present, they will form a white precipitate with the Ba2+ ions from the BaCl2