Question

Explain the tests for the presence o
Hydrogen, carbon-dioxide, Nitrogen
dioxide and oxygen with chemical
equations.
4:11​

Answer 1

Explanation:

Background

We've all been there; you have a bunch of unknown gases trapped in test tubes, and you need to figure out what you're dealing with. Okay, maybe we haven't all been there, but there are some nifty ways you can identify gases by using burning splits, limewater, or litmus paper. Most of the gases we'll focus on are colorless and odorless, so it's not possible to identify them by appearance.

In order to perform the tests, you'll need the following supplies:

Test tube of mysterious gas (with a stopper, so the gas doesn't escape)

Wooden splints

Matches

Goggles

Limewater (we'll go over the prep for this later)

Rubber tubing, glass rod, and a one-holed stopper

Litmus paper

Hydrogen

The first gas we will focus on is hydrogen, which is a non-toxic, colorless, odorless gas that's the most abundant element in the universe. Before we test for hydrogen, remember to wear your goggles for all of these tests. They'll protect you if the test tube breaks.

Here are the steps you need to take in order to test for hydrogen gas:

Light the wooden splint

Remove the stopper from the test tube and place the burning splint near the opening of the test tube

If hydrogen is present, you will hear a popping sound

Extinguish the splint

So, why the popping sound? When exposed to the flame, the hydrogen gas in the test tube reacts with the oxygen gas in the air. This reaction releases energy and that results in the popping soun

.Oxygen

We are going to use the splint again to test for oxygen, which is a non-toxic, colorless, odorless gas that you need to breathe in order to survive.

The directions for testing oxygen are a little different than for hydrogen, so pay attention:

Light the splint and then blow it out so it is glowing, but not an open flame

Remove the stopper from the test tube

Place the glowing splint into the test tube

If the splint reignites, the test is positive for oxygen

Extinguish the splint

Oxygen is responsible for combustion (burning of the splint), but normal atmospheric oxygen levels (around 21%) aren't enough to reignite the glowing splint. The test tube contains a higher percentage of oxygen, so when the glowing splint is placed inside, it's able to reignite.

Carbon Dioxide

The third gas we are going to test is carbon dioxide, which is colorless, odorless and you're breathing it out right now. It's also the stuff that makes your soda fizzy. There are a couple of easy ways to identify carbon dioxide gas.

Let's go over the first:

Light a splint

Remove the stopper from the test tube

Place the lit splint into the test tube

Answer 2

Explanation:

Tests for gases

Hydrogen, oxygen, carbon dioxide, ammonia and chlorine can be identified using different tests.

Hydrogen

A lighted wooden splint makes a popping sound in a test tube of hydrogen.

Oxygen

A glowing wooden splint relights in a test tube of oxygen.

Carbon dioxide

Carbon dioxide turns limewater milky. A lighted wooden splint goes out in a test tube of carbon dioxide but this happens with other gases, too. So the limewater test is a better choice.

Ammonia

Ammonia has a characteristic sharp, choking smell. It also makes damp red litmus paper turn blue. Ammonia forms a white smoke of ammonium chloride when hydrogen chloride gas, from concentrated hydrochloric acid, is held near it.

Chlorine

Chlorine has a characteristic sharp, choking smell. It also makes damp blue litmus paper turn red, and then bleaches it white. Chlorine makes damp starch-iodide paper turn blue-black.