C4.2

Question 1

How do you detect CO2?

Answer 1

Use limewater (calcium hydroxide)
If CO2 is present it will turn cloudy (a white precipitate is formed)

Question 2

How do you test for chlorine?

Answer 2

1) Take damp litmus paper
2) Hold near the substance
3) If chlorine is present it turns red - white

Question 3

How do you test for hydrogen?

Answer 3

Place a lighted splint near the mouth of the gas
Should make ansqueaky pop

Question 4

How do you test for oxygen?

Answer 4

Take a little splint and it should relight

Question 5

How do you test for sulfate ions?

Answer 5

1) add a few drops of dilute hydrochloric acid
2) add a few drops of barium chloride
3) if sulfate ions are presenta white precipitate should form

Question 6

How do you test for carbonate ions?

Answer 6

1) add a few drops pf dilute hydrochloric acid
2) if carbonate ions are present the bubbles of gas will be produced

Question 7

How do you test for Halide ions?

Answer 7

1) add a few drops of dilute nitric acid
2) add a few drops of silver nitrate solution
3) a precipitate will from if any of the halides are present:
- chloride, white precipitate
- bromide, cream precipitate
- iodide, yellow precipitate

Question 8

What are instrumental methods of analysis?

Answer 8

Use of a machine to carry out analysis of a substance

Question 9

What are the advantages of instrumental analysis?

Answer 9

High sensitivity - useful if the substance is expensive or hard to obtain
Good accuracy
Fast - can run quickly and all the time

Question 10

What is a mass spectrometer?

Answer 10

Measures the masses of atoms and molecules

Question 11

How do you interpret a mass spectrum?

Answer 11

• each peak represents a fragment of a molecule
• the peak on the far right represents the molecular ion
  The mass : charge = relative formula mass of the molecule