Identification of Common Gases Flashcards
All 21 cards in this deck
What is the test for hydrogen gas?
Hold a burning (lit) splint at the open end of a test tube of the gas.
What is the positive result of the test for hydrogen gas?
The gas burns rapidly with a (squeaky) pop sound.
True or false? A glowing splint is used to test for hydrogen.
False. A burning (lit) splint is used for hydrogen; a glowing splint is the test for oxygen.
Which gas test would you use on the gas given off when a metal reacts with a dilute acid, and what would you see?
A burning splint at the mouth of the tube; it burns with a squeaky pop, showing hydrogen.
What are the steps to test a gas for hydrogen?
e.g. the gas given off when magnesium reacts with dilute hydrochloric acid
- Collect the gas in a test tube.
- Hold a burning splint at the open end of the tube.
- A squeaky pop shows the gas is hydrogen.
What is the test for oxygen gas?
Insert a glowing splint into a test tube of the gas.
What is the positive result of the test for oxygen gas?
The glowing splint relights.
True or false? Oxygen is flammable and burns with a pop in the splint test.
False. Oxygen does not burn; it supports combustion, so it relights a glowing splint.
An unknown gas relights a glowing splint. Which gas is it, and how do you know it is not hydrogen?
Oxygen. Hydrogen would burn with a squeaky pop with a burning splint, not relight a glowing splint.
True or false? The test for oxygen is that a burning splint relights.
False. Oxygen relights a glowing splint, not a burning one.
What is the test for carbon dioxide gas?
Bubble the gas through (or shake it with) limewater.
Limewater is an aqueous solution of which compound?
Calcium hydroxide.
What is the positive result of the limewater test for carbon dioxide?
The limewater turns milky (cloudy).
True or false? Limewater turns milky because a white precipitate of calcium carbonate forms.
True. Carbon dioxide reacts with the calcium hydroxide to make insoluble calcium carbonate.
Which gas test would you use on the gas given off when a carbonate reacts with a dilute acid, and what would you see?
Bubble it through limewater; the limewater turns milky, showing carbon dioxide.
What are the steps to test a gas for carbon dioxide?
e.g. the gas given off when calcium carbonate reacts with dilute hydrochloric acid
- Collect the gas in a test tube.
- Bubble the gas through limewater (aqueous calcium hydroxide).
- Limewater turning milky (cloudy) shows the gas is carbon dioxide.
What is the test for chlorine gas?
Put damp litmus paper into the gas.
What is the positive result of the test for chlorine gas?
The litmus paper is bleached (turns white).
True or false? Dry litmus paper can be used to test for chlorine.
False. The litmus paper must be damp for the chlorine to bleach it.
True or false? 'The litmus paper turns red' is the accepted result for the chlorine test.
False. The accepted result is that the paper is bleached / turns white.
An unknown gas bleaches damp litmus paper white. Which gas is it, and how do you know it is not carbon dioxide?
Chlorine. Carbon dioxide may turn damp litmus red but does not bleach it; it would turn limewater milky.