Idenitfying Products Flashcards
What is the method for conducting a flame test?
Light a Bunsen burned so it’s just blue (just off safety)
Dip a soaked splint or wire loop in the sample
Hold the splint/loop in the flame
Observe and record the colour
What colour is a copper flame test?
Blue-green
What colour is a calcium flame test?
Orange-red
What colour is a potassium flame test?
Lilac
What colour is a lithium flame test?
Red
What colour is a sodium flame test?
Yellow
How do you test for oxygen gas?
Put a glowing splint into the test tube
If oxygen is present, the splint will relight
How do you test for hydrogen gas?
Put a lit splint into the test tube
If it makes a squeaky pop hydrogen is present
How do you test for carbon dioxide?
Bubble the gas through limewater
If the limewater goes cloudy/milky white, carbon dioxide is present
How do you test for chlorine gas?
Hold damp litmus paper in the test tube
If it turns white, chlorine gas is present
How do you test for aqueous metal ions?
Add dilute sodium hydroxide to the solution
Some metal hydroxides are insoluble precipitates
What is the precipitate colour of iron (II) when added to sodium hydroxide?
Green
What is the precipitate colour of iron (III) when added to sodium hydroxide?
Orange-brown
What is the precipitate colour of copper (II) when added to sodium hydroxide?
Blue
What is the precipitate colour of calcium (II) when added to sodium hydroxide?
White
What is the precipitate colour of zinc (II) when added to sodium hydroxide?
White
How do you tell the difference between zinc and calcium when testing for aqueous metal ions?
Add excess sodium hydroxide
Calcium precipitate is unchanged
Zine precipitate dissolves to form colourless solution
How do you test for carbonate ions?
Add dilute hydrochloric acid to the test tube
If bubbles form, carbonate ions are present (bubbles are carbon dioxide)
Test that the bubbles are carbon dioxide by using limewater
How do you test for halide ions?
Add some dilute nitric acid to the test tube
Add silver nitrate solution to the test tube
Why is dilute nitric acid added to the sample before silver nitrate when testing for halide ions?
Carbonate ions produce a white precipitate with silver nitrate, therefore the acid reacts with any carbonate ions present and removes them so there isn’t an incorrect positive result
What colour do chloride ions become when added to silver nitrate?
White
What colour do bromide ions turn when added to silver nitrate?
Cream
What colour do iodide ions turn when added to silver nitrate?
Yellow
How do you test for sulfate ions?
Add a few drops of hydrochloric acid to sample
Add dilute barium chloride solution
If a white precipitate forms sulfate ions are present
Why do you add hydrochloric acid before barium chloride when testing for sulfate ions?
Carbonate ions react with barium chloride to form a white precipitate, therefore the acid reacts with any carbonate ions present and removes them so there isn’t an incorrect positive result
What colour precipitate is formed when barium chloride is added to sulphate ions?
White
Why do you need to clean the wire loop before conducting a flame test?
In case any substance from previous is on it, therefore causing a false positive result
