Chemical tests Flashcards
What is the test for Hydrogen gas?
Lit splint, and a squeaky pop.
How do you test for Oxygen gas?
A glowing splint that relights
What is the test for Chlorine gas?
Litmus paper - Damp litmus paper bleaches (turns white).
What is the test for Ammonia gas?
Litmus paper - Turns damp red litmus paper blue.
What is the test for Carbon Dioxide gas?
Limewater - goes from colourless to milky/white
Describe the procedure for a flame test
- Use a clean Nichrome wire
- heat it
- dip in HCL
- collect a small sample of the compound and observe the flame’s color.
What flame color indicates the presence of Lithium ions (Li+)?
Red Flame
What flame color indicates the presence of Sodium ions (Na+)?
Yellow Flame
Which cation produces a lilac flame in a flame test?
Potassium ions (K+).
What flame color indicates the presence of Copper(II) ions (Cu2+)?
Blue-green flame.
How do you test for Ammonium ions (NH4+)?
Using sodium hydroxide solution and heating it
What is the result of a hydroxide test for Copper(II) ions (Cu2+)?
Light blue precipitate formed.
What is the color of the precipitate formed in the hydroxide test for Iron(III) ions (Fe3+)?
Red-brown precipitate
How do you test for Carbonate ions (CO3 2-)?
Add dilute acid, observe effervescence, and test the released gas, which turns limewater milky.
What is the result of a chloride ion test using acidified silver nitrate solution?
White precipitate formed
How do you test for Sulfate ions (SO4 2-)?
Acidify with dilute nitric acid and add aqueous barium nitrate, resulting in a white precipitate.
How can you physically test whether a sample of water is pure?
Check its boiling point; pure water should have a boiling point of exactly 100 degrees Celsius.
Describe the test for the presence of water using anhydrous copper(II) sulfate.
Anhydrous copper(II) sulfate is white; when water is present, it turns blue.
What effect do impurities generally have on the boiling point of a substance?
Impurities tend to raise the boiling point.
What is the color of the flame in a flame test for Potassium ions (K+)?
Lilac
What is the result for the presence of Bromide ions (Br-) using acidified silver nitrate solution?
Cream precipitate formed.
Describe a chemical test to show that a substance contains ammonium ions
- add sodium hydroxide solution and warm
- Test ammonia with damp red litmus paper
- Turns blue
Describe a chemical test to show that a substance contains chloride ions
- Add silver nitrate
- Add dilute nitric acid
- White precipitate forms
Suggest what property of hydrogen makes it suitable for filling balloons
LOW DENSITY
Suggest what property of helium that makes it more suitable than hydrogen for filling balloons
Non-flammable
Identify the pungent-smelling gas given off and explain why the red litmus paper must be damp before it is used
- Ammonia
- because water is needed to form hydroxide ions
Why is it important that the platinum wire is clean
Impurities may affect the colour
Why is it important to use a non-luminous flame?
Color can easily be seen
Why is a luminous Bunsen flame not suitable for carrying out a flame test?
It is difficult to see the color produced by the substance
Why should the platinum wire be cleaned between each test?
To remove any substance that may affect the color
How do you test for halide ions?
- acidify using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution. The following precipitates will be formed:
- chloride ions give a white precipitate of silver chloride
- bromide ions give a cream precipitate of silver bromide
- iodide ions give a yellow precipitate of silver iodide
