Idenitfying Products

Question 1

What is the method for conducting a flame test?

Answer 1

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

Question 2

What colour is a copper flame test?

Answer 2

Blue-green

Question 3

What colour is a calcium flame test?

Answer 3

Orange-red

Question 4

What colour is a potassium flame test?

Answer 4

Lilac

Question 5

What colour is a lithium flame test?

Answer 5

Red

Question 6

What colour is a sodium flame test?

Answer 6

Yellow

Question 7

How do you test for oxygen gas?

Answer 7

Put a glowing splint into the test tube

If oxygen is present, the splint will relight

Question 8

How do you test for hydrogen gas?

Answer 8

Put a lit splint into the test tube

If it makes a squeaky pop hydrogen is present

Question 9

How do you test for carbon dioxide?

Answer 9

Bubble the gas through limewater

If the limewater goes cloudy/milky white, carbon dioxide is present

Question 10

How do you test for chlorine gas?

Answer 10

Hold damp litmus paper in the test tube

If it turns white, chlorine gas is present

Question 11

How do you test for aqueous metal ions?

Answer 11

Add dilute sodium hydroxide to the solution

Some metal hydroxides are insoluble precipitates

Question 12

What is the precipitate colour of iron (II) when added to sodium hydroxide?

Answer 12

Green

Question 13

What is the precipitate colour of iron (III) when added to sodium hydroxide?

Answer 13

Orange-brown

Question 14

What is the precipitate colour of copper (II) when added to sodium hydroxide?

Answer 14

Blue

Question 15

What is the precipitate colour of calcium (II) when added to sodium hydroxide?

Answer 15

White

Question 16

What is the precipitate colour of zinc (II) when added to sodium hydroxide?

Answer 16

White

Question 17

How do you tell the difference between zinc and calcium when testing for aqueous metal ions?

Answer 17

Add excess sodium hydroxide
Calcium precipitate is unchanged
Zine precipitate dissolves to form colourless solution

Question 18

How do you test for carbonate ions?

Answer 18

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

Question 19

How do you test for halide ions?

Answer 19

Add some dilute nitric acid to the test tube

Add silver nitrate solution to the test tube

Question 20

Why is dilute nitric acid added to the sample before silver nitrate when testing for halide ions?

Answer 20

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

Question 21

What colour do chloride ions become when added to silver nitrate?

Answer 21

White

Question 22

What colour do bromide ions turn when added to silver nitrate?

Answer 22

Cream

Question 23

What colour do iodide ions turn when added to silver nitrate?

Answer 23

Yellow

Question 24

How do you test for sulfate ions?

Answer 24

Add a few drops of hydrochloric acid to sample
Add dilute barium chloride solution
If a white precipitate forms sulfate ions are present

Question 25

Why do you add hydrochloric acid before barium chloride when testing for sulfate ions?

Answer 25

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

Question 26

What colour precipitate is formed when barium chloride is added to sulphate ions?

Answer 26

White

Question 27

Why do you need to clean the wire loop before conducting a flame test?

Answer 27

In case any substance from previous is on it, therefore causing a false positive result