C3 Titrations, Energy, Chemical Tests. Flashcards
What ion is there when a brown precipitate forms after adding sodium hydroxide?
Brown precipitate means iron 3+ ions.
How so to start the positive metal test for ions?
Add sodium hydroxide (NaOH) to the unknown substance and you will get a coloured or white precipitate.
What ion is there when a green precipitate that turns brown, forms after adding sodium hydroxide?
Iron 2+ ions.
What ion is there when a blue precipitate forms after adding sodium hydroxide?
Copper 2+ ions.
When a white precipitate forms after adding sodium hydroxide, what are the possible ions?
Calcium 2+
Aluminium 3+
Magnesium 2+
When more sodium hydroxide is added to a white precipitate and it dissolves, what is the ion?
Aluminium 3+
If the flame test provides a brick red flame, what is the ion?
Calcium 2+
If the flame test provides no flame colour, what is the ion?
Magnesium 2+
If the flame test provides a crimson flame, what is the ion?
Lithium +
If the flame test provides a lilac flame, what is the ion?
Potassium +
If the flame test provides a green flame, what is the ion?
Barium 2+
If the flame test provides a yellow flame , what is the ion?
Sodium +
How is the flame test carried out?
Dip a nichrome wire in hydraulic acid, heat it and then put it in more acid so to clean it.
Put a small amount of the compound to be tested on the end of the loop.
Put the loop in the blue part of a Brunson burner. (Hottest part)
How can negative ions be rested for?
Looking for carbonates,
Testing for halides,
Testing for sulphates.
How do you test for a carbonate?
Add a carbonate with acid. This will produce salt, water but most importantly CO2.
Put the gas through some lime water, and is it goes cloudy it means CO2 which means a carbonate.
