Test for Anions
What gas is released when a carbonate reacts with dilute acid?
Carbon dioxide
Which ion produces ammonia gas when warmed with sodium hydroxide solution?
Ammonium ion (NH₄⁺).
Which gas turns limewater milky
Carbon dioxide
What colour flame does lithium ion produce?
Red
Which ion forms a white ppt with NaOH but not with NH3?
Ca2+
What color precipitate forms when iodide ions react with silver nitrate after acidifying with nitric acid?
Yellow precipitate
Which cation forms a light blue precipitate with sodium hydroxide that is insoluble in excess?
Copper(II) ion (Cu²⁺)
Which gas turns damp red litmus paper blue?
Ammonia
Which metal ion gives a yellow flame?
Sodium ion Na+
A solution gives a white precipitate with both sodium hydroxide and ammonia, but it dissolves in excess of both reagents. Which ion is present?
Zinc ion (Zn²⁺)
Which halide ion forms a white precipitate with dil. nitric acid and silver nitrate?
Chloride
What color precipitate is formed by iron(III) ions with sodium hydroxide?
Red-brown precipitate
What is the positive test for hydrogen gas?
Produces a pop sound with lighted splint
When a flame test is conducted with a mystery solution a blue-green flame is produced. The lab tech says the solution contains barium. Is he right? If he is wrong, what cation does it actually contain?
Copper (II) Cu2+
Both sulfite and sulfur dioxide decolorize acidified potassium manganate(VII). How could you tell them apart through an experiment?
Sulfite is a solid or aqueous ion.
SO₂ is a gas.
Only SO₂ would turn litmus paper from purple to red
When a solution is reacted with dil. nitric acid and aqueous barium nitrate, a white precipitate is formed. What is the name of this white precipitate?
Barium sulfate (BaSO4)
Which cation forms a green precipitate with sodium hydroxide that is soluble in excess?
Chromium(III) ion (Cr³⁺)
How can you prove the presence of chlorine gas?
Bring a damp litmus paper near the mouth of the test tube. If chlorine is present, the litmus paper will be bleached.
What are some tools used to put a cation sample into a flame for testing?
Nichrome wire
Platinum wire
Splint
Two tests were done on two portions of solution X.
1-When flame test was conducted- lilac flame produced
2-When tested with with dil. nitric acid and silver nitrate- white precipitate produced.
What is the compound in solution?
Potassium Chloride
Into a solution, aluminium foil and sodium hydroxide is added and it is warmed gently. No gas is given off. When a damp red litmus paper is brought near the mouth of the test tube, it does not change colour. What anion is absent from this solution?
Nitrate ion (NO3-)
When sodium hydroxide is added dropwise to a solution and a white precipitate is formed. Which 2 cations might be present in the solution? Suggest an additional test to figure out which one it is.
Al3+ or Zn2+
Add excess aqueous ammonia. Al3+ will be insoluble and Zn2+ will dissolve to give colourless solution
A gas produced in a reaction is delivered into a purple coloured aqueous solution. The purple coloured solution becomes colourless. What is the gas produced and what is the purple solution?
Gas: Sulfur dioxide (SO2)
Purple-coloured solution:aqueous potassium manganate(VII)
What part of the flame do we put the wire/splint that holds the sample?
The non-luminous part/ The roaring part of the flame
A solution when tested with dil. nitric acid and silver nitrate, produced a cream precipitate.
When another portion of that same solution was tested with aqueous NaOH, a gas was given off.
What is the anion present? Suggest a test to confirm whether the gas given off is ammonia.
Anion: Br-
Test: Bring a damp red litmus paper near