Chemical Analysis Flashcards
What is the gas test for hydrogen?
A Burning Splint
What is the positive result for the hydrogen test?
The burning splint explodes with a pop
What is the gas test for oxygen?
A Glowing Splint
What is the positive result for the Oxygen test?
The glowing splint reignites
What is the gas test for Carbon Dioxide?
Limewater
What is the positive result for the Carbon Dioxide test?
Limewater turns cloudy.
What is the gas test for Chlorine?
Damp Blue Litmus
What is the positive result of the gas test for Chlorine?
The damp blue litmus turns red, then white.
What is the gas test for Ammonia (NH3)?
Damp Red Litmus
What is the positive result for the gas test for Ammonia
The damp red litmus turns blue
How does the burning splint tell us Hydrogen gas is made?
It makes hydrogen react with oxygen, which is highly EXOTHERMIC, and therefore creates the pop noise.
How does the Glowing Splint tell us Oxygen gas is made?
Oxygen is required for combustion, and the flame on the glowing splint is about to extinguish. If placed in oxygen, it will reignite. This tells us Oxygen gas is made.
How does limewater tell us Carbon Dioxide gas is made?
Limewater is Ca(OH)2. It reacts with Carbon Dioxide to make CaCO3, a white precipitate. Therefore the limewater turns cloudy.
How does the damp blue litmus tell us that Chlorine gas is made?
Chlorine reacts with water to make HCl. HCl reacts with indicator on the paper to go from blue (base) -> red (acid). If this happens Chlorine gas was made. Later, the Chloric acid will make the paper turn white.
How does the damp red litmus tell us that Ammonia (NH3) gas is made?
Ammonia is a base, and therefore it will react with the indicator on the paper, going from red (acid) -> blue (base). If this happens, Ammonia gas was made.
What is the basic method for a gas test?
Place each specific test inside a test tube producing an unknown gas, until one of them produces a positive result.
What color do Lithium compounds produce in the flame test?
Red
What color do Sodium compounds produce in the flame test?
Yellow/Orange
What color do Potassium compounds produce in the flame test?
Lilac
What color do Calcium compounds produce in the flame test?
Brick red
What color do Barium compounds produce in the flame test?
Light green or apple green
What color do Copper compounds produce in the flame test?
Blue/green
What is the basic method for the flame test?
- Clean needle with HCl until it doesn’t change the color of the flame
- Place needle in compound and then in fire
- Observe flame color
What result from the halide test tells us Chloride was present?
White precipitate
What result from the halide test tells us Bromide was present?
Cream precipitate
What result from the halide test tells us Iodide was present?
Yellow Precipitate
Which anion was present if the precipitate turns dark grey when exposed to Ultra-Violet light
Chloride
What is the basic method for a Halide Test
- Add Nitric Acid to remove Hydroxide and Carbonate ions
- Add SilverNitrate and observe precipitate
Why do we react SilverNitrate with the compound?
Because Silver Halides, which will be made if the unknown compound is soluble, are insoluble. Therefore it is a precipitation reaction, and we can identify which halide it is based on color of precipitate.
Example: what is the Ionic equation for the reaction:
(X = unknown anion)
AgNO3 + NaX –> AgX + NaNO3
Ag+ + X- –> AgX
What is the basic method to test for Ammonium (NH4+) Cations?
- Add NaOH and heat chemical
- If a gas is made, put damp red litmus in it
- Observe color of damp red litmus
What is the positive result for the Ammonium (NH4+) test?
Damp red litmus turns blue.
Why does the damp red litmus turn blue if Ammonium (NH4+) was present?
The reaction makes Ammonia (NH3). This is a base and. makes the indicator on the litmus go from red (acid) –> blue (base)
What gas is made if a burning splint explodes with a pop?
Hydrogen
What gas is made if a glowing splint reignites?
Oxygen
What gas is made if limewater goes cloudy?
Carbon Dioxide
What gas is made if damp blue litmus turns red then white?
Chlorine
What gas is made if damp red litmus turns blue
Ammonia (NH3)
What Cation is present if the flame turns red?
Lithium
What Cation is present if the flame turns yellow?
Sodium
What Cation is present if the flame turns lilac?
Potassium
What Cation is present if the flame turns brick red?
Calcium
What Cation is present if the flame turns light green?
Barium
What Cation is present if the flame turns blue/green?
Copper
What anion was present if the halide test turns white?
Chloride
What anion was present if the halide test turns cream?
Bromide
What anion was present if the halide test turns yellow?
Iodide.
Which cation was present if damp red litmus paper turns blue?
Ammonium (NH4+)
What is the basic method to test for nitrate?
- Add NaOH to the compound
- Add Al Powder and heat
- Place damp red litmus in gas
- Observe color of litmus paper
What is the positive result for the nitrate test?
Damp red litmus turns blue
Why does damp red litmus turn blue when exposed to nitrate compounds?
Nitrate compounds are bases. This means that the indicator on the litmus goes from red (acid) –> blue (base)
What is the basic method for the NaOH/NH3 tests (on other compounds)?
- dissolve sample in water
- add drops of NaOH / NH3 and observe precipitate
- Add excess drops of NH3 / NaOH and observe precipitate
Interpret these results for the NaOH and NH3 tests:
NaOH: colorless (aq)
Excess NaOH: colorless (aq)
NH3: colorless (aq)
Excess NH3: colorless (aq)
group 1 compound
Interpret these results for the NaOH and NH3 tests:
NaOH: white (s)
Excess NaOH: white (s)
NH3: white (s)
Excess NH3: white (s)
group 2 compound
Interpret these results for the NaOH and NH3 tests:
NaOH: green (s) –time-> orange (s)
Excess NaOH: green (s)
NH3: green (s)
Excess NH3: green (s)
Fe2+ compound
Interpret these results for the NaOH and NH3 tests:
NaOH: orange/brown (s)
Excess NaOH: orange/brown (s)
NH3: orange/brown (s)
Excess NH3: orange/brown (s)
Fe3+ compound
Interpret these results for the NaOH and NH3 tests:
NaOH: blue (s)
Excess NaOH: blue (aq). Redissolves
NH3: dark blue and white (s)
Excess NH3: dark blue (aq). Redissolves
Cu2+ compound
Interpret these results for the NaOH and NH3 tests:
NaOH: green/grey (s)
Excess NaOH: green/grey (s)
NH3: green/grey (s)
Excess NH3: green/grey (s)
Cr3+ compound
Interpret these results for the NaOH and NH3 tests:
NaOH: white (s)
Excess NaOH: colorless (aq)
NH3: white (s)
Excess NH3: colorless (aq)
Zn2+ compound
Interpret these results for the NaOH and NH3 tests:
NaOH: faint white (s)
Excess NaOH: colorless (aq)
NH3: faint white (s)
Excess NH3: faint white (s)
Al3+ compound
