C4.2.1 - Detecting Gases

Question 1

How do you detect carbon dioxide?

Answer 1

You use limewater as it is a calcium hydroxide solution and it turns cloudy white when carbon dioxide is bubbled through it

Question 2

Why does limewater show carbon dioxide?

Answer 2

The calcium hydroxide reacts with carbon dioxide to form water and a white precipitate of calcium carbonate

Question 3

How do you detect chlorine?

Answer 3

1. Use a drop of tap water to dampen a piece of blue litmus paper
2. Hold the paper near to a container that holds the substance
3. If chlorine is present, the paper turns red then white

Question 4

Why does the litmus paper turn red then white?

Answer 4

Because chlorine in water forms an acidic solution so the paper turns red but it also bleaches dye turning the paper white.

Question 5

How do you detect hydrogen?

Answer 5

Place a lighted splint near the mouth of the container of gas

If there is hydrogen then it should ignite with a squeaky pop

Question 6

How do you detect oxygen?

Answer 6

Place a glowing splint near the mouth of the container of gas

If oxygen is present the splint should relight