Tests for Anions Flashcards
What are the anions you can test for?
Carbonates, Sulfates and Halides.
What is the test for Carbonates?
1) use a pipette add drops of dilute acid to the test tube containing the unknown substance
2) connect the test tube to another one containing limewater
What is the positive result for a carbonate test?
The limewater goes from colourless to cloudy
Why does the limewater turn cloudy if carbonate ions are present?
When the carbonate ions are bubbled through the limewater, their reaction with the acid releases carbon dioxide, causing the limewater to turn cloudy.
Give a balanced example equation of a carbonate reaction.
Na2CO3(aq)+2HCl(aq) = CO2(g)+2NaCl(aq)+H20(l)
Sodium carbonate + HCl = CO2 + sodium chloride + water
What is the test for sulfates?
1) add a couple drops of dilute HCl followed by a couple drops of barium chloride to the test tube containing unknown substance
What is the positive result for a sulfate test?
A white precipitate of barium sulfate will form
Why is hydrochloric acid added to the substance first?
To get rid of any traces of carbonate ions before you do the test, so as to not confuse the results.
What is a precipitate?
A solid that is formed in a solution during a chemical reaction.
What is the test for halides?
1) add a couple drops of dilute nitric acid followed by a couple drops of silver nitrate solution to the unknown solution
What are the positive results for a halide test?
A chloride gives a white precipitate of silver chloride.
A bromide gives a cream precipitate of silver bromide.
An iodide gives a yellow precipitate of silver iodide.
