Test for Ions Flashcards
What acid is used to detect carbonates?
A dilute acid such as hydrochloric acid.
What will happen if a dilute acid is added to a carbonate?
Carbon dioxide will be released as bubbles or fizz.
How do you test for carbon dioxide?
Limewater will turn cloudy in the presence of CO2.
How do you use the limewater to test for CO2?
Bubble the gas released through a test tube of limewater.
What is the equation for the reaction of a carbonate and an acid?
CO3^3-(s) + 2H+(aq) = CO2(g) + H2O(l)
How do you test for sulfates?
Add dilute HCl followed by barium chloride solution.
Which sulfate is insoluble in water?
Barium sulfate
What will happen if a sulfate is present?
You will get a white precipitate.
What sulfate is the white precipitate?
Barium sulfate
What tells you that a sulfate is present?
Barium sulfate.
What is the equation for the reaction producing barium sulfate?
Ba2+(aq) +SO4^2-(aq) = BaSO4(s)
What is used to test for halides?
Add nitric acid and then silver nitrate solution.
What will happen in the halide test if chloride, bromide or iodide is present?
A precipitate will form.
What colour precipitate is formed if chloride is present?
A yellow precipitate of silver chloride.
What colour precipitate is formed if bromide is present?
A cream precipitate of silver bromide.
What colour precipitate is formed of iodide is present?
A yellow precipitate of silver iodide.
Why does fluoride give no precipitate when testing for halides?
Silver fluoride is soluble.
How do you tell the ppts of halides apart?
Test their solubility in ammonia.
Does AgCl dissolve in dilute NH3?
Yes
Does AgCl dissolve in concentrated NH3?
Yes
Does AgBr dissolve in dilute NH3?
No
Does AgBr dissolve in concentrated NH3?
Yes
Does AgI dissolve in dilute NH3?
No
Does AgI dissolve in concentrated NH3?
No
How do you test for ammonium compounds?
Use NaOH and damp litmus paper?
Why does the litmus paper have to be damp when testing for ammonia?
This is so that the ammonia gas can dissolve and make the colour change.
What colour litmus paper should be used to test for ammonium gas?
Red
What colour will the ammonium gas turn the litmus paper?
It will turn it blue.
Is ammonium gas acid or alkaline?
It is alkaline.
What does the NaOH and litmus paper test tell you about a compound?
It tells you whether or not a substance contains ammonium ions.
How do you carry out the test for ammonium compounds?
Add some sodium hydroxide to the test tube containing the sample and warm the mixture. If ammonia gas is given off, there are ammonium ions in the substance.
What is the equation for testing for ammonium compounds?
NH4+(aq) + OH-(aq) = NH3(g) + H2O(l)
What three compounds are insoluble?
Barium sulfate, barium carbonate and barium sulfite.
What is important when testing for sulfates?
You must make sure that no carbonate ions or sulfite are present first.
Why do you need to test for sulfate ions before halides?
This is because both sulfate and halide ions will produce ppts with silver nitrate.
What will adding dilute acid do to the test solution?
It will remove anions.
Which tests test for anions?
Carbonate, sulfate and halide tests.
Which test tests for cations?
NaOH and litmus paper
In what order should you test for anions?
Carbonates then sulfates then halides.
