Which method should be used to test for oxygen gas?

Which method should be used to test for chlorine gas?

Which method should be used to test for carbon dioxide gas?

Fred is testing an unknown gas. He places a lit split at the end of a test tube containing this gas. The lit splint goes out and Fred hears a 'squeaky pop'. Which gas was in the test tube?

Paula is testing an unknown gas. She places a glowing split at the end of a test tube containing this gas. The glowing splint relights. Which gas was in the test tube?

Tim is testing an unknown gas. He places a piece of damp blue litmus paper into end of a test tube containing this gas. The blue litmus paper goes red then white. Which gas was in the test tube?

Zoe is testing an unknown gas. She bubbles the gas through a tube into a container of limewater. The limewater goes cloudy. Which gas was in the test tube?

The picture shows the results of chromatography of a purple felt tip pen. Which ink colour is the most soluble?