Gas Tests
With a glowing splint that reignites
How do we test for the presence of oxygen?
Carbonates
What anion is present if white precipitate is formed in limewater test?
blue-green flame
What flame colour is shown in the presence of copper (II) ions?
Green
What colour precipitate do we get when testing for Iron (II) ions?
chlorine, hydrogen and sodium hydroxide
what are the products of electrolysis of brine?
Using a lit splint will give a small explosion
How do we test for the presence of hydrogen?
A white precipitate of barium sulfate
What is the result when testing for presence of sulfate?
brick-red
What flame colour show the presence of calcium ions?
Sodium Hydroxide
What chemical do you add when testing for cations?
Positive electrode: potassium
Negative electrode: bromide
What are the products in the electrode during electrolysis of potassium bromide?
Pungent odour and turns litmus paper to blue
How to test presence of ammonia gas?
Pale yellow precipitate
What is the positive result for and iodide (when reacted with Nitric acid and silver nitrate)?
Do not produce a characteristic colour.
What is the colour of magnesium in flame test?
Zinc and aluminium ions
What ions will form white precipitate in drops of sodium hydroxide but re-dissolves in excess?
graphite
What is the commonly used electrode since it is inert and conduct electricity?
Cloudy
Base (sodium hydroxide) + aluminium + heat
What is the procedure in test for nitrates?
To prevent contaminants
Why do you soak the wire in acid before doing a flame test?
Calcium and magnesium
Which ions give a white precipitate when reacted with sodium hydroxide and does not redissolve in excess?
What property do we use during fractional distillation of petrochemicals?
Red then white
What colour will blue litmus paper turn in the presence of chlorine?
potassium chloride
What substance will give a lilac flame and a cream precipitate?
The colours will mix.
Why it is difficult to conduct a flame test with multiple cations?
A yellow precipitate for halide tests
And a yellow flame test
What are the test results for sodium iodide?
condenser
What do we use to turn the evaporated gas to liquid again?